Study planner
90-Day Data Engineer Study Plan
90 days, 348 planned hours: 3 hours on weekdays and 6 at weekends. Build foundations first, then reliable pipelines and interview readiness. Every day includes a hands-on exercise, an interview question and a clear outcome.
Days completed0 of 90 days
Set a Saturday start date to align the 6-hour weekend and 3-hour weekday schedule with calendar dates. Saved in this browser only.
Phase 1: Foundations
Build SQL, DSA, Python and core data-engineering foundations; finish one batch project and begin applications.
Week 1Use SQL filtering, NULL handling and aggregation; solve 20 array/hash problems; explain core pipeline foundations; run the idempotent CSV loader locally.
Daily focusStart here
Day 1/ 90
Idempotent CSV loader setup and replay check
Plan progress, day 10 of 90 days- SQLSELECT, WHERE & basic filtering
- SQLDaily Active Users case study
- SQL practice175. Combine Two Tables ↗
- DSAMajority Element
- DSAFind Pivot Index
- DSASubarray Sum Equals K
- DSASubarray Sums Divisible by K
- DE ConceptsData lifecycle and ownership
- PythonIdempotent CSV loader setup and replay check
- ReviewWeekly review and interview recall
- Exercise
- Load a CSV into local Postgres twice and show that the second run creates no duplicate rows.
- Interview question
- How would you implement Idempotent CSV loader setup and replay check so it handles malformed input, retries and repeat runs safely?
- Outcome
- You can explain Idempotent CSV loader setup and replay check, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 1
Day 2/ 90
Local Postgres setup and CSV load
Plan progress, day 20 of 90 days- SQLAggregate functions (SUM, AVG, MIN, MAX)
- SQLGROUP BY fundamentals
- SQLMonthly Revenue case study
- SQL practice584. Find Customer Referee ↗
- DSAMaximum Subarray
- DSAMaximum Product Subarray
- DSAMaximum Subarray Sum with One Deletion
- PythonLocal Postgres setup and CSV load
- DE ConceptsFoundations lab: OLTP and OLAP workloads
- ReviewWeekly review and interview recall
- Exercise
- Load a CSV into local Postgres twice and show that the second run creates no duplicate rows.
- Interview question
- How would you implement Local Postgres setup and CSV load so it handles malformed input, retries and repeat runs safely?
- Outcome
- You can explain Local Postgres setup and CSV load, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 1
Day 3/ 90
Python for data engineering
Plan progress, day 30 of 90 days- SQLHAVING vs WHERE
- SQL practice595. Big Countries ↗
- DSAMaximum Absolute Sum of Any Subarray
- DSAMaximum Sum Circular Subarray
- DSAProduct of Array Except Self
- DSAContiguous Array
- DSAFind All Numbers Disappeared in an Array
- DE ConceptsBatch versus streaming
- PythonPython for data engineering
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Python for data engineering and keep a short note of the result.
- Interview question
- How would you implement Python for data engineering so it handles malformed input, retries and repeat runs safely?
- Outcome
- You can explain Python for data engineering, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 1
Day 4/ 90
Reusable functions and modules
Plan progress, day 40 of 90 days- SQLDISTINCT and de-duplication
- SQLNULL handling with IS NULL / COALESCE
- SQL practice1148. Article Views I ↗
- DSARotate Image
- DSASpiral Matrix
- DSAShortest Subarray with Sum at Least K
- DSAFind All Duplicates in an Array
- DE ConceptsETL versus ELT
- PythonReusable functions and modules
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Reusable functions and modules and keep a short note of the result.
- Interview question
- How would you implement Reusable functions and modules so it handles malformed input, retries and repeat runs safely?
- Outcome
- You can explain Reusable functions and modules, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 1
Day 5/ 90
CSV and JSON file handling
Plan progress, day 50 of 90 days- SQLORDER BY multi-column sorting
- SQL practice1683. Invalid Tweets ↗
- DSASet Matrix Zeroes
- DSAMissing Number
- DE ConceptsPython functions and reusable code
- DE ConceptsFoundations lab: Data lifecycle and ownership
- DE ConceptsOLTP and OLAP workloads
- DE ConceptsCSV and JSON trade-offs
- PythonCSV and JSON file handling
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for CSV and JSON file handling and keep a short note of the result.
- Interview question
- How would you implement CSV and JSON file handling so it handles malformed input, retries and repeat runs safely?
- Outcome
- You can explain CSV and JSON file handling, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 1
Day 6/ 90
Iterators and generators
Plan progress, day 60 of 90 days- SQLLIMIT / TOP / FETCH FIRST
- SQL practice1378. Replace Employee ID With The Unique Identifier ↗
- DSASet Mismatch
- DE ConceptsPython iterators and generators
- PythonIterators and generators
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Iterators and generators and keep a short note of the result.
- Interview question
- How would you implement Iterators and generators so it handles malformed input, retries and repeat runs safely?
- Outcome
- You can explain Iterators and generators, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 1
Day 7/ 90
Error handling and logging
Plan progress, day 70 of 90 days- SQLCASE WHEN expressions
- SQL practice1068. Product Sales Analysis I ↗
- DSAFirst Missing Positive
- DE ConceptsPython CSV validation
- PythonError handling and logging
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Error handling and logging and keep a short note of the result.
- Interview question
- How would you implement Error handling and logging so it handles malformed input, retries and repeat runs safely?
- Outcome
- You can explain Error handling and logging, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Week 2Solve 20 more DSA problems; join data safely, explain common file formats, define warehouse grain, and describe basic S3/IAM access.
Daily focusWeek 2
Day 8/ 90
Compare file formats and inspect a partitioned data layout
Plan progress, day 80 of 90 days- SQLINNER JOIN basics
- SQLLEFT JOIN basics
- SQLCustomer Lifetime Value case study
- SQL practice1581. Customer Who Visited but Did Not Make Any Transactions ↗
- DSAContains Duplicate
- DSAValid Anagram
- DSATwo Sum
- DSAFirst Unique Character in a String
- DSALongest Palindrome
- Project / labCompare file formats and inspect a partitioned data layout
- DE ConceptsFoundations lab: CSV and JSON trade-offs
- ReviewWeekly review and interview recall
- Exercise
- Extend the csv to warehouse pipeline with a tested, replay-safe step and record the result.
- Interview question
- How would you explain and apply Compare file formats and inspect a partitioned data layout in a production data-engineering workflow?
- Outcome
- You can explain Compare file formats and inspect a partitioned data layout, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 2
Day 9/ 90
Compare file formats and inspect a partitioned data layout
Plan progress, day 90 of 90 days- SQLRIGHT JOIN & FULL OUTER JOIN
- SQLSelf Join patterns
- SQLChurn Rate case study
- SQL practice197. Rising Temperature ↗
- DSARansom Note
- DSAValid Sudoku
- DSAGroup Anagrams
- DSALongest Consecutive Sequence
- DSALongest Common Prefix
- DE ConceptsParquet and columnar storage
- Project / labCompare file formats and inspect a partitioned data layout
- DE ConceptsFoundations lab: Parquet and columnar storage
- ReviewWeekly review and interview recall
- Exercise
- Extend the csv to warehouse pipeline with a tested, replay-safe step and record the result.
- Interview question
- How would you explain and apply Compare file formats and inspect a partitioned data layout in a production data-engineering workflow?
- Outcome
- You can explain Compare file formats and inspect a partitioned data layout, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 2
Day 10/ 90
Grain definition
Plan progress, day 100 of 90 days- SQLAnti-join (NOT EXISTS / LEFT JOIN NULL)
- SQLMulti-table joins
- SQL practice1661. Average Time of Process per Machine ↗
- DSAReverse String
- DSAEncode and Decode Strings
- DE ConceptsAvro and schema evolution
- Data ModelingGrain definition
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Grain definition and keep a short note of the result.
- Interview question
- How would you apply Grain definition to a warehouse with changing business requirements?
- Outcome
- You can explain Grain definition, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 2
Day 11/ 90
S3 buckets & objects
Plan progress, day 110 of 90 days- SQLSubqueries in WHERE
- SQLSubqueries in FROM (derived tables)
- SQL practice577. Employee Bonus ↗
- DSAString to Integer (atoi)
- DSANumber of 1 Bits
- DE ConceptsPartitioning and data layout
- AWSS3 buckets & objects
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for S3 buckets & objects and keep a short note of the result.
- Interview question
- How would you design access, retries and monitoring around S3 buckets & objects in an AWS data pipeline?
- Outcome
- You can explain S3 buckets & objects, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 2
Day 12/ 90
Storage classes
Plan progress, day 120 of 90 days- SQLCorrelated subqueries
- SQLCommon Table Expressions (CTEs)
- SQL practice1280. Students and Examinations ↗
- DSAReverse Bits
- DSASingle Number
- DE ConceptsWarehouse grain and star schemas
- AWSStorage classes
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Storage classes and keep a short note of the result.
- Interview question
- How would you design access, retries and monitoring around Storage classes in an AWS data pipeline?
- Outcome
- You can explain Storage classes, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 2
Day 13/ 90
Star Schema
Plan progress, day 130 of 90 days- SQLMultiple chained CTEs
- SQLPIVOT rows to columns
- SQL practice570. Managers with at Least 5 Direct Reports ↗
- DSACounting Bits
- DSAComplement of Base 10 Integer
- DE ConceptsFact and dimension tables
- Data ModelingStar Schema
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Star Schema and keep a short note of the result.
- Interview question
- How would you apply Star Schema to a warehouse with changing business requirements?
- Outcome
- You can explain Star Schema, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 2
Day 14/ 90
Fact tables
Plan progress, day 140 of 90 days- SQLWindow function basics (OVER)
- SQLPARTITION BY clause
- SQL practice1934. Confirmation Rate ↗
- DSASum of Two Integers
- DSASingle Number III
- DE ConceptsSlowly changing dimensions
- Data ModelingFact tables
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Fact tables and keep a short note of the result.
- Interview question
- How would you apply Fact tables to a warehouse with changing business requirements?
- Outcome
- You can explain Fact tables, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Week 3Build DataFrame transformations and explain lazy evaluation, SCD types and partitioning trade-offs.
Daily focusWeek 3
Day 15/ 90
DataFrame API basics
Plan progress, day 150 of 90 days- SQLROW_NUMBER()
- SQLRANK() vs DENSE_RANK()
- SQLAverage Order Value case study
- SQL practice620. Not Boring Movies ↗
- DSAValid Palindrome II
- DSAValid Palindrome
- DSAMove Zeroes
- DSARemove Duplicates from Sorted Array
- DSASquares of a Sorted Array
- DE ConceptsIncremental loading and watermarks
- PySparkDataFrame API basics
- DE ConceptsFoundations lab: Incremental loading and watermarks
- ReviewWeekly review and interview recall
- Exercise
- Build a small DataFrame exercise for DataFrame API basics and verify the result on a local sample.
- Interview question
- How does DataFrame API basics affect execution, partitioning and failure recovery in Spark?
- Outcome
- You can explain DataFrame API basics, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 3
Day 16/ 90
Spark architecture (driver/executor)
Plan progress, day 160 of 90 days- SQLLAG() and LEAD()
- SQLConversion Funnel case study
- SQL practice1251. Average Selling Price ↗
- DSASegregate 0s and 1s
- DSABackspace String Compare
- DSATwo Sum II Input Array Is Sorted
- DSA3Sum
- DSAContainer With Most Water
- DE ConceptsIdempotent pipeline writes
- PySparkSpark architecture (driver/executor)
- DE ConceptsFoundations lab: Idempotent pipeline writes
- ReviewWeekly review and interview recall
- Exercise
- Build a small DataFrame exercise for Spark architecture (driver/executor) and verify the result on a local sample.
- Interview question
- How does Spark architecture (driver/executor) affect execution, partitioning and failure recovery in Spark?
- Outcome
- You can explain Spark architecture (driver/executor), complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 3
Day 17/ 90
Lazy evaluation & DAG
Plan progress, day 170 of 90 days- SQLRunning totals with SUM OVER
- SQL practice1075. Project Employees I ↗
- DSASort Colors
- DSA3Sum Closest
- DE ConceptsChange data capture patterns
- PySparkLazy evaluation & DAG
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Lazy evaluation & DAG and keep a short note of the result.
- Interview question
- How does Lazy evaluation & DAG affect execution, partitioning and failure recovery in Spark?
- Outcome
- You can explain Lazy evaluation & DAG, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 3
Day 18/ 90
Joins in Spark SQL
Plan progress, day 180 of 90 days- SQLDate truncation & bucketing
- SQL practice1633. Percentage of Users Attended a Contest ↗
- DSATriplets with Smaller Sum
- DSASubarray Product Less Than K
- DE ConceptsData quality checks and contracts
- PySparkJoins in Spark SQL
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Joins in Spark SQL and keep a short note of the result.
- Interview question
- How does Joins in Spark SQL affect execution, partitioning and failure recovery in Spark?
- Outcome
- You can explain Joins in Spark SQL, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 3
Day 19/ 90
Reading/writing Parquet
Plan progress, day 190 of 90 days- SQLTop-N per group
- SQL practice1211. Queries Quality and Percentage ↗
- DSA4Sum
- DSAShortest Unsorted Continuous Subarray
- DE ConceptsTesting pipelines and CI/CD
- PySparkReading/writing Parquet
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Reading/writing Parquet and keep a short note of the result.
- Interview question
- How does Reading/writing Parquet affect execution, partitioning and failure recovery in Spark?
- Outcome
- You can explain Reading/writing Parquet, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 3
Day 20/ 90
SCD Type 2 (history)
Plan progress, day 200 of 90 days- SQLDeduplicate keeping latest record
- SQL practice1193. Monthly Transactions I ↗
- DSATrapping Rain Water
- DSAImplement Stack using Queues
- DE ConceptsRetries and failure recovery
- Data ModelingSCD Type 2 (history)
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for SCD Type 2 (history) and keep a short note of the result.
- Interview question
- How would you apply SCD Type 2 (history) to a warehouse with changing business requirements?
- Outcome
- You can explain SCD Type 2 (history), complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 3
Day 21/ 90
Partitions & parallelism
Plan progress, day 210 of 90 days- SQLAliases and column naming
- SQL practice1174. Immediate Food Delivery II ↗
- DSAImplement Queue using Stacks
- DSANumber of Recent Calls
- DE ConceptsPipeline observability
- PySparkPartitions & parallelism
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Partitions & parallelism and keep a short note of the result.
- Interview question
- How does Partitions & parallelism affect execution, partitioning and failure recovery in Spark?
- Outcome
- You can explain Partitions & parallelism, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Week 4Explain the system-design method and sketch a batch ingestion framework after learning the storage foundations.
Daily focusWeek 4
Day 22/ 90
Declare a warehouse grain and sketch a star schema
Plan progress, day 220 of 90 days- SQLComparison & logical operators
- SQLNew vs Returning Customers case study
- SQL practice550. Game Play Analysis IV ↗
- DSADesign Circular Queue
- DSABest Time to Buy and Sell Stock
- DSAMax Sum Subarray of Size K
- DSALongest Substring Without Repeating Characters
- DSALongest Repeating Character Replacement
- DE ConceptsLate data and backfills
- Project / labDeclare a warehouse grain and sketch a star schema
- DE ConceptsFoundations lab: Late data and backfills
- ReviewWeekly review and interview recall
- Exercise
- Extend the csv to warehouse pipeline with a tested, replay-safe step and record the result.
- Interview question
- How would you explain and apply Declare a warehouse grain and sketch a star schema in a production data-engineering workflow?
- Outcome
- You can explain Declare a warehouse grain and sketch a star schema, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 4
Day 23/ 90
Declare a warehouse grain and sketch a star schema
Plan progress, day 230 of 90 days- SQLIN, BETWEEN, LIKE patterns
- SQLTop Selling Products case study
- SQL practice2356. Number of Unique Subjects Taught by Each Teacher ↗
- DSAPermutation in String
- DSAMinimum Size Subarray Sum
- DSALongest K unique characters substring
- DSAFruit Into Baskets
- DSAMax Consecutive Ones III
- DE ConceptsStorage layers and raw landing
- Project / labDeclare a warehouse grain and sketch a star schema
- DE ConceptsFoundations lab: Storage layers and raw landing
- ReviewWeekly review and interview recall
- Exercise
- Extend the csv to warehouse pipeline with a tested, replay-safe step and record the result.
- Interview question
- How would you explain and apply Declare a warehouse grain and sketch a star schema in a production data-engineering workflow?
- Outcome
- You can explain Declare a warehouse grain and sketch a star schema, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 4
Day 24/ 90
Three-layer architecture
Plan progress, day 240 of 90 days- SQLString functions (CONCAT, SUBSTRING, TRIM)
- SQL practice1070. Product Sales Analysis III ↗
- DSAFind All Anagrams in a String
- DSAMinimum Window Substring
- DE ConceptsPython API pagination
- SnowflakeThree-layer architecture
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Three-layer architecture and keep a short note of the result.
- Interview question
- How would you use Three-layer architecture while controlling query performance, access and cost?
- Outcome
- You can explain Three-layer architecture, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 4
Day 25/ 90
File formats & staging
Plan progress, day 250 of 90 days- SQLDate functions basics
- SQL practice596. Classes More Than 5 Students ↗
- DSASliding Window Maximum
- DSASubstring with Concatenation of All Words
- DE ConceptsData normalization trade-offs
- SnowflakeFile formats & staging
- SnowflakeCOPY INTO command
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for File formats & staging and keep a short note of the result.
- Interview question
- How would you use File formats & staging while controlling query performance, access and cost?
- Outcome
- You can explain File formats & staging, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 4
Day 26/ 90
DAG fundamentals
Plan progress, day 260 of 90 days- SQLCAST and data type conversion
- SQL practice586. Customer Placing the Largest Number of Orders ↗
- DSAValid Parentheses
- DSARemove All Adjacent Duplicates In String
- DE ConceptsLake, warehouse and lakehouse
- AirflowDAG fundamentals
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for DAG fundamentals and keep a short note of the result.
- Interview question
- How would you apply DAG fundamentals to a pipeline that must recover safely after a task failure?
- Outcome
- You can explain DAG fundamentals, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 4
Day 27/ 90
Design a batch ingestion framework
Plan progress, day 270 of 90 days- SQLArithmetic & rounding
- SQL practice610. Triangle Judgment ↗
- DSAMin Stack
- DSAEvaluate Reverse Polish Notation
- DE ConceptsData modeling methods
- System DesignDesign a batch ingestion framework
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Design a batch ingestion framework and keep a short note of the result.
- Interview question
- How would you design a production data platform for Design a batch ingestion framework, including scale, failure handling and trade-offs?
- Outcome
- You can explain Design a batch ingestion framework, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 4
Day 28/ 90
Joins in Spark SQL
Plan progress, day 280 of 90 days- SQLCOUNT vs COUNT(DISTINCT)
- SQL practice1978. Employees Whose Manager Left the Company ↗
- DSARemove All Adjacent Duplicates in String II
- DSASimplify Path
- DE ConceptsSecure data access and PII
- PySparkJoins in Spark SQL
- PySparkReading/writing Parquet
- AirflowBackfills & reruns
- AirflowIdempotent tasks
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Joins in Spark SQL and keep a short note of the result.
- Interview question
- How does Joins in Spark SQL affect execution, partitioning and failure recovery in Spark?
- Outcome
- You can explain Joins in Spark SQL, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Week 5Implement incremental, replay-safe loads; explain CDC and Airflow backfills; start the warehouse pipeline project.
Daily focusWeek 5
Day 29/ 90
CSV to warehouse pipeline: day 29 lab
Plan progress, day 290 of 90 days- SQLConditional aggregation
- SQLInventory Turnover case study
- SQL practice1045. Customers Who Bought All Products ↗
- DSANext Greater Element I
- DSADaily Temperatures
- DSACar Fleet
- DSANext Greater Element II
- DSARemove Nodes From Linked List
- DE ConceptsIncremental loading and watermarks
- Project / labCSV to warehouse pipeline: day 29 lab
- System DesignDesign a batch ingestion framework
- ReviewWeekly review and interview recall
- Exercise
- Extend the csv to warehouse pipeline with a tested, replay-safe step and record the result.
- Interview question
- How would you explain and apply CSV to warehouse pipeline: day 29 lab in a production data-engineering workflow?
- Outcome
- You can explain CSV to warehouse pipeline: day 29 lab, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 5
Day 30/ 90
E-commerce analytics platform: day 30 lab
Plan progress, day 300 of 90 days- SQLUNION vs UNION ALL
- SQLEmployee Hierarchy case study
- SQL practice1731. The Number of Employees Which Report to Each Employee ↗
- DSARemove K Digits
- DSA132 Pattern
- DSALargest Rectangle in Histogram
- DSABinary Search
- DSACeil in Sorted Array
- DE ConceptsIdempotent pipeline writes
- Project / labE-commerce analytics platform: day 30 lab
- System DesignDesign a Data Lake on cloud object storage
- ReviewWeekly review and interview recall
- Exercise
- Extend the e-commerce analytics platform with a tested, replay-safe step and record the result.
- Interview question
- How would you explain and apply E-commerce analytics platform: day 30 lab in a production data-engineering workflow?
- Outcome
- You can explain E-commerce analytics platform: day 30 lab, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Month review and Mock 1: explain the batch project, SQL and DSA foundations; make a realistic application plan.
Phase 2: Core pipelines
Build reliable batch and CDC pipelines, practise cloud and warehouse work, and complete a second project.
Week 5Implement incremental, replay-safe loads; explain CDC and Airflow backfills; start the warehouse pipeline project.
Daily focusWeek 5
Day 31/ 90
Retries & alerting
Plan progress, day 310 of 90 days- SQLEXCEPT / INTERSECT set operations
- SQL practice1789. Primary Department for Each Employee ↗
- DSATime Based Key-Value Store
- DSAFind First and Last Position
- DE ConceptsChange data capture patterns
- AirflowRetries & alerting
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Retries & alerting and keep a short note of the result.
- Interview question
- How would you apply Retries & alerting to a pipeline that must recover safely after a task failure?
- Outcome
- You can explain Retries & alerting, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 5
Day 32/ 90
Glue bookmarks
Plan progress, day 320 of 90 days- SQLCross Join & cartesian products
- SQL practice1741. Find Total Time Spent by Each Employee ↗
- DSANumber of Occurrence
- DSAMedian of Two Sorted Arrays
- DE ConceptsData quality checks and contracts
- AWSGlue bookmarks
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Glue bookmarks and keep a short note of the result.
- Interview question
- How would you design access, retries and monitoring around Glue bookmarks in an AWS data pipeline?
- Outcome
- You can explain Glue bookmarks, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 5
Day 33/ 90
Glue Data Quality
Plan progress, day 330 of 90 days- SQLSemi-join with EXISTS
- SQL practice511. Game Play Analysis I ↗
- DSAFind Rotation Count
- DSAFind Minimum in Rotated Sorted Array
- DE ConceptsRetries and failure recovery
- AWSGlue Data Quality
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Glue Data Quality and keep a short note of the result.
- Interview question
- How would you design access, retries and monitoring around Glue Data Quality in an AWS data pipeline?
- Outcome
- You can explain Glue Data Quality, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 5
Day 34/ 90
Backfills & reruns
Plan progress, day 340 of 90 days- SQLLATERAL / CROSS APPLY joins
- SQL practice176. Second Highest Salary ↗
- DSASearch in Rotated Sorted Array
- DSAPeak Index in a Mountain Array
- DE ConceptsLate data and backfills
- AirflowBackfills & reruns
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Backfills & reruns and keep a short note of the result.
- Interview question
- How would you apply Backfills & reruns to a pipeline that must recover safely after a task failure?
- Outcome
- You can explain Backfills & reruns, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 5
Day 35/ 90
Testing DAGs
Plan progress, day 350 of 90 days- SQLScalar subqueries
- SQL practice1757. Recyclable and Low Fat Products ↗
- DSAFind Peak Element
- DSAKoko Eating Bananas
- DE ConceptsTesting pipelines and CI/CD
- AirflowTesting DAGs
- AirflowCI/CD for DAGs
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Testing DAGs and keep a short note of the result.
- Interview question
- How would you apply Testing DAGs to a pipeline that must recover safely after a task failure?
- Outcome
- You can explain Testing DAGs, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Week 6Explain Delta Lake transactions and schema evolution, load data into a warehouse, and design a medallion lakehouse.
Daily focusWeek 6
Day 36/ 90
Delta Lake architecture
Plan progress, day 360 of 90 days- SQLUNPIVOT columns to rows
- SQLFraud Pattern Detection case study
- SQL practice1907. Count Salary Categories ↗
- DSAMinimum Number of Days to Make m Bouquets
- DSAAggressive Cows
- DSAMaximum Candies Allocated to K Children
- DSACapacity To Ship Packages Within D Days
- DSASplit Array Largest Sum
- DE ConceptsPython iterators and generators
- PySparkChange data capture pipeline: day 36 lab
- PySparkDelta Lake architecture
- PySparkACID transactions on Delta
- System DesignDesign a Lakehouse (bronze/silver/gold)
- ReviewWeekly review and interview recall
- Exercise
- Build a small DataFrame exercise for Delta Lake architecture and verify the result on a local sample.
- Interview question
- How does Delta Lake architecture affect execution, partitioning and failure recovery in Spark?
- Outcome
- You can explain Delta Lake architecture, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 6
Day 37/ 90
Schema evolution
Plan progress, day 370 of 90 days- SQLPivoting dynamic columns
- SQLSession Duration case study
- SQL practice1667. Fix Names in a Table ↗
- DSASearch a 2D Matrix
- DSASearch a 2D Matrix II
- DSAKth Smallest Element in a Sorted Matrix
- DSAMerge Two Sorted Lists
- DSARemove Nth Node From End of List
- DE ConceptsPython CSV validation
- PySparkFraud detection pipeline: day 37 lab
- PySparkSchema evolution
- PySparkMERGE / upsert
- System DesignDesign a CDC pipeline from OLTP to warehouse
- ReviewWeekly review and interview recall
- Exercise
- Build a small DataFrame exercise for Schema evolution and verify the result on a local sample.
- Interview question
- How does Schema evolution affect execution, partitioning and failure recovery in Spark?
- Outcome
- You can explain Schema evolution, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 6
Day 38/ 90
COPY INTO command
Plan progress, day 380 of 90 days- SQLGROUPING SETS
- SQL practice1527. Patients With a Condition ↗
- DSACopy List with Random Pointer
- DSAAdd Two Numbers
- DE ConceptsCSV and JSON trade-offs
- SnowflakeCOPY INTO command
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for COPY INTO command and keep a short note of the result.
- Interview question
- How would you use COPY INTO command while controlling query performance, access and cost?
- Outcome
- You can explain COPY INTO command, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 6
Day 39/ 90
Snowpipe continuous ingestion
Plan progress, day 390 of 90 days- SQLROLLUP and CUBE
- SQL practice1517. Find Users With Valid E-Mails ↗
- DSALRU Cache
- DSALinked List Cycle
- DE ConceptsParquet and columnar storage
- SnowflakeSnowpipe continuous ingestion
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Snowpipe continuous ingestion and keep a short note of the result.
- Interview question
- How would you use Snowpipe continuous ingestion while controlling query performance, access and cost?
- Outcome
- You can explain Snowpipe continuous ingestion, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 6
Day 40/ 90
Glue ETL jobs (Spark)
Plan progress, day 400 of 90 days- SQLNTILE() bucketing
- SQL practice1327. List the Products Ordered in a Period ↗
- DSAHappy Number
- DSAMiddle of the Linked List
- DE ConceptsAvro and schema evolution
- AWSGlue ETL jobs (Spark)
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Glue ETL jobs (Spark) and keep a short note of the result.
- Interview question
- How would you design access, retries and monitoring around Glue ETL jobs (Spark) in an AWS data pipeline?
- Outcome
- You can explain Glue ETL jobs (Spark), complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 6
Day 41/ 90
Athena basics
Plan progress, day 410 of 90 days- SQLFIRST_VALUE / LAST_VALUE
- SQL practice262. Trips and Users ↗
- DSAPalindrome Linked List
- DSAReorder List
- DE ConceptsPartitioning and data layout
- AWSAthena basics
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Athena basics and keep a short note of the result.
- Interview question
- How would you design access, retries and monitoring around Athena basics in an AWS data pipeline?
- Outcome
- You can explain Athena basics, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 6
Day 42/ 90
Design a Lakehouse (bronze/silver/gold)
Plan progress, day 420 of 90 days- SQLMoving average with frame clause
- SQL practice1084. Sales Analysis III ↗
- DSAFind the Duplicate Number
- DSALinked List Cycle II
- DE ConceptsWarehouse grain and star schemas
- System DesignDesign a Lakehouse (bronze/silver/gold)
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Design a Lakehouse (bronze/silver/gold) and keep a short note of the result.
- Interview question
- How would you design a production data platform for Design a Lakehouse (bronze/silver/gold), including scale, failure handling and trade-offs?
- Outcome
- You can explain Design a Lakehouse (bronze/silver/gold), complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Week 7Explain Kafka delivery basics, data contracts and quality checks; design an idempotent CDC pipeline.
Daily focusWeek 7
Day 43/ 90
Topic fundamentals
Plan progress, day 430 of 90 days- SQLConditional window frames
- SQLA/B Test Results case study
- SQL practice1141. User Activity for the Past 30 Days I ↗
- DSACircular Array Loop
- DSAReverse Linked List
- DSAReverse Linked List II
- DSASwap Nodes in Pairs
- DSARotate List
- DE ConceptsData quality checks and contracts
- KafkaTopic fundamentals
- KafkaAdd a Kafka CDC lab to the warehouse pipeline
- System DesignDesign a real-time streaming platform
- ReviewWeekly review and interview recall
- Exercise
- Create a producer/consumer walkthrough, record the offset, then replay one message safely.
- Interview question
- How would you use Topic fundamentals and explain its ordering, delivery and replay guarantees?
- Outcome
- You can explain Topic fundamentals, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 7
Day 44/ 90
At-least-once
Plan progress, day 440 of 90 days- SQLPercent of total
- SQLSubscription Renewals case study
- SQL practice1204. Last Person to Fit in the Bus ↗
- DSAReverse Nodes in k-Group
- DSAInvert Binary Tree
- DSAMaximum Depth of Binary Tree
- DSADiameter of Binary Tree
- DSABalanced Binary Tree
- DE ConceptsIdempotent pipeline writes
- KafkaKafka/Spark/Delta streaming pipeline: day 44 lab
- KafkaAt-least-once
- System DesignDesign an event-driven architecture
- ReviewWeekly review and interview recall
- Exercise
- Create a producer/consumer walkthrough, record the offset, then replay one message safely.
- Interview question
- How would you use At-least-once and explain its ordering, delivery and replay guarantees?
- Outcome
- You can explain At-least-once, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 7
Day 45/ 90
CDC with streams
Plan progress, day 450 of 90 days- SQLCumulative distribution
- SQL practice1164. Product Price at a Given Date ↗
- DSASame Tree
- DSASubtree of Another Tree
- DE ConceptsChange data capture patterns
- SnowflakeCDC with streams
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for CDC with streams and keep a short note of the result.
- Interview question
- How would you use CDC with streams while controlling query performance, access and cost?
- Outcome
- You can explain CDC with streams, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 7
Day 46/ 90
Scheduled tasks (CRON)
Plan progress, day 460 of 90 days- SQLMedian & percentile (PERCENTILE_CONT)
- SQL practice1077. Project Employees III ↗
- DSACount Good Nodes in Binary Tree
- DSAConstruct Tree from Preorder and Inorder
- DE ConceptsIdempotent pipeline writes
- SnowflakeScheduled tasks (CRON)
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Scheduled tasks (CRON) and keep a short note of the result.
- Interview question
- How would you use Scheduled tasks (CRON) while controlling query performance, access and cost?
- Outcome
- You can explain Scheduled tasks (CRON), complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 7
Day 47/ 90
XCom push/pull
Plan progress, day 470 of 90 days- SQLGenerate date series / calendar table
- SQL practice1321. Restaurant Growth ↗
- DSALowest Common Ancestor of Binary Tree
- DSABinary Tree Maximum Path Sum
- DE ConceptsChange data capture patterns
- AirflowXCom push/pull
- AirflowTaskFlow API
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for XCom push/pull and keep a short note of the result.
- Interview question
- How would you apply XCom push/pull to a pipeline that must recover safely after a task failure?
- Outcome
- You can explain XCom push/pull, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 7
Day 48/ 90
Redshift architecture
Plan progress, day 480 of 90 days- SQLYear-over-year growth
- SQL practice1341. Movie Rating ↗
- DSASerialize and Deserialize Binary Tree
- DSABinary Tree Level Order Traversal
- DE ConceptsData quality checks and contracts
- AWSRedshift architecture
- AWSRedshift Spectrum
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Redshift architecture and keep a short note of the result.
- Interview question
- How would you design access, retries and monitoring around Redshift architecture in an AWS data pipeline?
- Outcome
- You can explain Redshift architecture, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 7
Day 49/ 90
Partition keys & ordering
Plan progress, day 490 of 90 days- SQLMonth-over-month change
- SQL practice1393. Capital Gain/Loss ↗
- DSABinary Tree Right Side View
- DSAImplement Trie (Prefix Tree)
- DE ConceptsTesting pipelines and CI/CD
- KafkaPartition keys & ordering
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Partition keys & ordering and keep a short note of the result.
- Interview question
- How would you use Partition keys & ordering and explain its ordering, delivery and replay guarantees?
- Outcome
- You can explain Partition keys & ordering, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Week 8Tune Spark, describe CI/CD and observability, and complete two SQL/DSA or data-engineering mocks.
Daily focusWeek 8
Day 50/ 90
Exactly-once semantics (EOS)
Plan progress, day 500 of 90 days- SQLRolling 7/30 day metrics
- SQLRefund Analysis case study
- SQL practice1158. Market Analysis I ↗
- DSADesign Add and Search Words
- DSAExtra Characters in a String
- DSASearch Suggestions System
- DSAWord Search II
- DSAConvert Sorted Array to BST
- DE ConceptsData quality checks and contracts
- KafkaLarge-scale batch processing: day 50 lab
- KafkaExactly-once semantics (EOS)
- System DesignDesign an analytics / BI platform
- ReviewWeekly review and interview recall
- Exercise
- Create a producer/consumer walkthrough, record the offset, then replay one message safely.
- Interview question
- How would you use Exactly-once semantics (EOS) and explain its ordering, delivery and replay guarantees?
- Outcome
- You can explain Exactly-once semantics (EOS), complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 8
Day 51/ 90
Connect framework
Plan progress, day 510 of 90 days- SQLSlowly changing dimension queries
- SQLLead Scoring case study
- SQL practice180. Consecutive Numbers ↗
- DSAValidate Binary Search Tree
- DSAKth Smallest Element in a BST
- DSALowest Common Ancestor of a BST
- DSAInsert into a BST
- DSADelete Node in a BST
- DE ConceptsTesting pipelines and CI/CD
- KafkaReal-time analytics pipeline: day 51 lab
- KafkaConnect framework
- KafkaSource vs sink connectors
- System DesignDesign a Customer 360 platform
- ReviewWeekly review and interview recall
- Exercise
- Create a producer/consumer walkthrough, record the offset, then replay one message safely.
- Interview question
- How would you use Connect framework and explain its ordering, delivery and replay guarantees?
- Outcome
- You can explain Connect framework, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 8
Day 52/ 90
AQE (Adaptive Query Execution)
Plan progress, day 520 of 90 days- SQLRecursive CTEs
- SQL practice182. Duplicate Emails ↗
- DSAKth Largest Element in a Stream
- DSALast Stone Weight
- DE ConceptsPipeline observability
- PySparkAQE (Adaptive Query Execution)
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for AQE (Adaptive Query Execution) and keep a short note of the result.
- Interview question
- How does AQE (Adaptive Query Execution) affect execution, partitioning and failure recovery in Spark?
- Outcome
- You can explain AQE (Adaptive Query Execution), complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 8
Day 53/ 90
Persistence & caching levels
Plan progress, day 530 of 90 days- SQLHierarchical / org-chart queries
- SQL practice184. Department Highest Salary ↗
- DSATop K Frequent Elements
- DSAK Closest Points to Origin
- DE ConceptsRetries and failure recovery
- PySparkPersistence & caching levels
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Persistence & caching levels and keep a short note of the result.
- Interview question
- How does Persistence & caching levels affect execution, partitioning and failure recovery in Spark?
- Outcome
- You can explain Persistence & caching levels, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 8
Day 54/ 90
EMR clusters
Plan progress, day 540 of 90 days- SQLGraph traversal in SQL
- SQL practice185. Department Top Three Salaries ↗
- DSAKth Largest Element in an Array
- DSATask Scheduler
- DE ConceptsChange data capture patterns
- AWSEMR clusters
- AWSLambda + S3/Kinesis
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for EMR clusters and keep a short note of the result.
- Interview question
- How would you design access, retries and monitoring around EMR clusters in an AWS data pipeline?
- Outcome
- You can explain EMR clusters, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 8
Day 55/ 90
Debezium CDC
Plan progress, day 550 of 90 days- SQLGaps and Islands problem
- SQL practice196. Delete Duplicate Emails ↗
- DSAMin Cost to Connect Ropes
- DSASort Characters By Frequency
- DE ConceptsLate data and backfills
- KafkaDebezium CDC
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Debezium CDC and keep a short note of the result.
- Interview question
- How would you use Debezium CDC and explain its ordering, delivery and replay guarantees?
- Outcome
- You can explain Debezium CDC, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 8
Day 56/ 90
Kinesis Data Streams
Plan progress, day 560 of 90 days- SQLDetecting consecutive streaks
- DSAFind K Closest Elements
- DSAReorganize String
- DE ConceptsData quality checks and contracts
- AWSKinesis Data Streams
- AWSMetrics & alarms
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Kinesis Data Streams and keep a short note of the result.
- Interview question
- How would you design access, retries and monitoring around Kinesis Data Streams in an AWS data pipeline?
- Outcome
- You can explain Kinesis Data Streams, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Week 9Explain streaming state and watermarks, complete a streaming project extension, and defend a clickstream design.
Daily focusWeek 9
Day 57/ 90
Design a GDPR/PII compliant pipeline
Plan progress, day 570 of 90 days- SQLSessionization of events
- SQLDaily Active Users case study
- DSAMaximum Frequency Stack
- DSAMaximum Sum Combination
- DSAFind Median from Data Stream
- DSASliding Window Median
- DE ConceptsData modeling methods
- System DesignS3/PySpark/Snowflake pipeline: day 57 lab
- System DesignDesign a GDPR/PII compliant pipeline
- System DesignDesign a fraud detection pipeline
- ReviewWeekly review and interview recall
- Exercise
- Extend the s3/pyspark/snowflake pipeline with a tested, replay-safe step and record the result.
- Interview question
- How would you design a production data platform for Design a GDPR/PII compliant pipeline, including scale, failure handling and trade-offs?
- Outcome
- You can explain Design a GDPR/PII compliant pipeline, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 9
Day 58/ 90
Consumer lag
Plan progress, day 580 of 90 days- SQLRetention analysis
- SQLMonthly Revenue case study
- DSAIPO
- DSADesign Twitter
- DSAMerge k Sorted Lists
- DSASmallest Range Covering Elements from K Lists
- DE ConceptsSecure data access and PII
- KafkaCSV to warehouse pipeline: day 58 lab
- KafkaConsumer lag
- KafkaRebalancing protocols
- System DesignDesign a recommendation data pipeline
- ReviewWeekly review and interview recall
- Exercise
- Create a producer/consumer walkthrough, record the offset, then replay one message safely.
- Interview question
- How would you use Consumer lag and explain its ordering, delivery and replay guarantees?
- Outcome
- You can explain Consumer lag, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 9
Day 59/ 90
Design a data quality framework
Plan progress, day 590 of 90 days- SQLCohort analysis
- DSAJump Game
- DSAJump Game II
- DE ConceptsReplay-safe event processing
- System DesignDesign a data quality framework
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Design a data quality framework and keep a short note of the result.
- Interview question
- How would you design a production data platform for Design a data quality framework, including scale, failure handling and trade-offs?
- Outcome
- You can explain Design a data quality framework, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 9
Day 60/ 90
Design a data observability system
Plan progress, day 600 of 90 days- SQLFunnel / conversion analysis
- DSAGas Station
- DSAHand of Straights
- DE ConceptsCost and freshness trade-offs
- System DesignDesign a data observability system
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Design a data observability system and keep a short note of the result.
- Interview question
- How would you design a production data platform for Design a data observability system, including scale, failure handling and trade-offs?
- Outcome
- You can explain Design a data observability system, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Mocks 2 and 3: complete SQL/DSA and data-engineering design rounds; review gaps from the pipeline project.
Phase 3: Advanced and interview-ready
Practise streaming, system design and mock interviews; finish a project demo, résumé and portfolio.
Week 9Explain streaming state and watermarks, complete a streaming project extension, and defend a clickstream design.
Daily focusWeek 9
Day 61/ 90
Structured Streaming model
Plan progress, day 610 of 90 days- SQLFirst & last touch attribution
- DSAMerge Triplets to Form Target
- DSAPartition Labels
- DE ConceptsData lifecycle and ownership
- PySparkStructured Streaming model
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Structured Streaming model and keep a short note of the result.
- Interview question
- How does Structured Streaming model affect execution, partitioning and failure recovery in Spark?
- Outcome
- You can explain Structured Streaming model, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 9
Day 62/ 90
Watermarking
Plan progress, day 620 of 90 days- SQLMarket basket / co-occurrence
- DSAValid Parenthesis String
- DSAMaximum Length of Pair Chain
- DE ConceptsOLTP and OLAP workloads
- PySparkWatermarking
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Watermarking and keep a short note of the result.
- Interview question
- How does Watermarking affect execution, partitioning and failure recovery in Spark?
- Outcome
- You can explain Watermarking, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 9
Day 63/ 90
Stateful aggregations
Plan progress, day 630 of 90 days- SQLJSON parsing in SQL
- DSAMinimum Add to Make Parentheses Valid
- DSARemove Duplicate Letters
- DE ConceptsBatch versus streaming
- PySparkStateful aggregations
- PySparkExactly-once in streaming
- PySparkExtend the clickstream project with watermarks and stateful aggregation
- System DesignDesign a clickstream analytics pipeline
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Extend the clickstream project with a watermark and stateful aggregation; record a replay test.
- Interview question
- How does Stateful aggregations affect execution, partitioning and failure recovery in Spark?
- Outcome
- You can explain Stateful aggregations, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Week 10Solve timed SQL/DSA sets and design a governed pipeline with quality and observability controls.
Daily focusWeek 10
Day 64/ 90
RBAC model
Plan progress, day 640 of 90 days- SQLArray & nested data handling
- SQLCustomer Lifetime Value case study
- DSAMeeting Rooms
- DSAMerge Intervals
- DSAInsert Interval
- DSANon-overlapping Intervals
- DE ConceptsETL versus ELT
- SnowflakeE-commerce analytics platform: day 64 lab
- SnowflakeRBAC model
- SnowflakeColumn-level security / masking
- System DesignDesign a GDPR/PII compliant pipeline
- ReviewWeekly review and interview recall
- Exercise
- Extend the e-commerce analytics platform with a tested, replay-safe step and record the result.
- Interview question
- How would you use RBAC model while controlling query performance, access and cost?
- Outcome
- You can explain RBAC model, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 10
Day 65/ 90
Lake Formation basics
Plan progress, day 650 of 90 days- SQLRegex matching in SQL
- SQLChurn Rate case study
- DSAInterval List Intersections
- DSAMeeting Rooms II
- DSAMy Calendar I
- DSAGenerate Parentheses
- DE ConceptsPython functions and reusable code
- AWSChange data capture pipeline: day 65 lab
- AWSLake Formation basics
- AWSLF-Tags
- System DesignDesign a feature store
- ReviewWeekly review and interview recall
- Exercise
- Extend the change data capture pipeline with a tested, replay-safe step and record the result.
- Interview question
- How would you design access, retries and monitoring around Lake Formation basics in an AWS data pipeline?
- Outcome
- You can explain Lake Formation basics, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 10
Day 66/ 90
Design a data catalog & lineage system
Plan progress, day 660 of 90 days- SQLQuery optimization & cost reduction
- DSASubsets
- DSAPermutations
- DE ConceptsPython iterators and generators
- System DesignDesign a data catalog & lineage system
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Design a data catalog & lineage system and keep a short note of the result.
- Interview question
- How would you design a production data platform for Design a data catalog & lineage system, including scale, failure handling and trade-offs?
- Outcome
- You can explain Design a data catalog & lineage system, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 10
Day 67/ 90
Design a data observability system
Plan progress, day 670 of 90 days- SQLReading EXPLAIN / execution plans
- DSASubsets II
- DSALetter Combinations of a Phone Number
- DE ConceptsPython CSV validation
- System DesignDesign a data observability system
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Design a data observability system and keep a short note of the result.
- Interview question
- How would you design a production data platform for Design a data observability system, including scale, failure handling and trade-offs?
- Outcome
- You can explain Design a data observability system, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 10
Day 68/ 90
Time Travel basics
Plan progress, day 680 of 90 days- SQLQuery rewriting for performance
- DSALetter Case Permutation
- DSACombination Sum
- DE ConceptsCSV and JSON trade-offs
- SnowflakeTime Travel basics
- SnowflakeCredit consumption analysis
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Time Travel basics and keep a short note of the result.
- Interview question
- How would you use Time Travel basics while controlling query performance, access and cost?
- Outcome
- You can explain Time Travel basics, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 10
Day 69/ 90
Cost Explorer & budgets
Plan progress, day 690 of 90 days- SQLAvoiding full table scans
- DSACombination Sum II
- DSAWord Search
- DE ConceptsParquet and columnar storage
- AWSCost Explorer & budgets
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Cost Explorer & budgets and keep a short note of the result.
- Interview question
- How would you design access, retries and monitoring around Cost Explorer & budgets in an AWS data pipeline?
- Outcome
- You can explain Cost Explorer & budgets, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 10
Day 70/ 90
Design a data SLA & freshness monitoring system
Plan progress, day 700 of 90 days- SQLAnti-pattern detection
- DSAPalindrome Partitioning
- DSAN-Queens
- DE ConceptsAvro and schema evolution
- System DesignDesign a data SLA & freshness monitoring system
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Design a data SLA & freshness monitoring system and keep a short note of the result.
- Interview question
- How would you design a production data platform for Design a data SLA & freshness monitoring system, including scale, failure handling and trade-offs?
- Outcome
- You can explain Design a data SLA & freshness monitoring system, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Week 11Handle late data, retries and backfills in system-design interviews; explain operating costs and failure modes.
Daily focusWeek 11
Day 71/ 90
LocalExecutor
Plan progress, day 710 of 90 days- SQLIndex design (B-tree, composite)
- SQLAverage Order Value case study
- DSASudoku Solver
- DSAFind if Path Exists in Graph
- DSAClone Graph
- DSANumber of Provinces
- DE ConceptsLate data and backfills
- AirflowFraud detection pipeline: day 71 lab
- AirflowLocalExecutor
- AirflowCeleryExecutor
- System DesignDesign a metrics / KPI platform
- ReviewWeekly review and interview recall
- Exercise
- Extend the fraud detection pipeline with a tested, replay-safe step and record the result.
- Interview question
- How would you apply LocalExecutor to a pipeline that must recover safely after a task failure?
- Outcome
- You can explain LocalExecutor, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 11
Day 72/ 90
Backfills & reruns
Plan progress, day 720 of 90 days- SQLCovering indexes
- SQLConversion Funnel case study
- DSAWord Ladder
- DSAReconstruct Itinerary
- DSAFlood Fill
- DSAIsland Perimeter
- DE ConceptsRetries and failure recovery
- AirflowKafka/Spark/Delta streaming pipeline: day 72 lab
- AirflowBackfills & reruns
- AirflowRetries & alerting
- System DesignDesign an ELT pipeline with dbt
- ReviewWeekly review and interview recall
- Exercise
- Extend the kafka/spark/delta streaming pipeline with a tested, replay-safe step and record the result.
- Interview question
- How would you apply Backfills & reruns to a pipeline that must recover safely after a task failure?
- Outcome
- You can explain Backfills & reruns, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 11
Day 73/ 90
Consumer lag
Plan progress, day 730 of 90 days- SQLIndex selectivity & cardinality
- DSANumber of Islands
- DSAMax Area of Island
- DE ConceptsPipeline observability
- KafkaConsumer lag
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Consumer lag and keep a short note of the result.
- Interview question
- How would you use Consumer lag and explain its ordering, delivery and replay guarantees?
- Outcome
- You can explain Consumer lag, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 11
Day 74/ 90
Rebalancing protocols
Plan progress, day 740 of 90 days- SQLBitmap indexing
- DSAPacific Atlantic Water Flow
- DSASurrounded Regions
- DE ConceptsSlowly changing dimensions
- KafkaRebalancing protocols
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Rebalancing protocols and keep a short note of the result.
- Interview question
- How would you use Rebalancing protocols and explain its ordering, delivery and replay guarantees?
- Outcome
- You can explain Rebalancing protocols, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 11
Day 75/ 90
Time Travel basics
Plan progress, day 750 of 90 days- SQLPartitioning strategies
- DSARotting Oranges
- DSANumber of Closed Islands
- DE ConceptsIncremental loading and watermarks
- SnowflakeTime Travel basics
- SnowflakeWarehouse right-sizing
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Time Travel basics and keep a short note of the result.
- Interview question
- How would you use Time Travel basics while controlling query performance, access and cost?
- Outcome
- You can explain Time Travel basics, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 11
Day 76/ 90
Design a backfill & late-data handling system
Plan progress, day 760 of 90 days- SQLPartition pruning
- DSACourse Schedule
- DSACourse Schedule II
- DE ConceptsIdempotent pipeline writes
- System DesignDesign a backfill & late-data handling system
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Design a backfill & late-data handling system and keep a short note of the result.
- Interview question
- How would you design a production data platform for Design a backfill & late-data handling system, including scale, failure handling and trade-offs?
- Outcome
- You can explain Design a backfill & late-data handling system, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 11
Day 77/ 90
CI/CD for DAGs
Plan progress, day 770 of 90 days- SQLMaterialized views
- DSATopological Sort
- DSAMinimum Height Trees
- DE ConceptsChange data capture patterns
- AirflowCI/CD for DAGs
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for CI/CD for DAGs and keep a short note of the result.
- Interview question
- How would you apply CI/CD for DAGs to a pipeline that must recover safely after a task failure?
- Outcome
- You can explain CI/CD for DAGs, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Week 12Complete two mocks, explain project trade-offs clearly, and identify remaining weak areas.
Daily focusWeek 12
Day 78/ 90
Design a multi-tenant data platform
Plan progress, day 780 of 90 days- SQLColumnar vs row storage
- SQLNew vs Returning Customers case study
- DSAAlien Dictionary
- DSAGraph Valid Tree
- DSANumber of Connected Components
- DSARedundant Connection
- DE ConceptsData quality checks and contracts
- System DesignLarge-scale batch processing: day 78 lab
- System DesignDesign a multi-tenant data platform
- System DesignDesign a data quality framework
- ReviewWeekly review and interview recall
- Exercise
- Extend the large-scale batch processing with a tested, replay-safe step and record the result.
- Interview question
- How would you design a production data platform for Design a multi-tenant data platform, including scale, failure handling and trade-offs?
- Outcome
- You can explain Design a multi-tenant data platform, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 12
Day 79/ 90
Design a data mesh architecture
Plan progress, day 790 of 90 days- SQLSharding & distributed SQL
- SQLTop Selling Products case study
- DSAIs Graph Bipartite?
- DSAPath With Minimum Effort
- DSANetwork Delay Time
- DSACheapest Flights Within K Stops
- DE ConceptsTesting pipelines and CI/CD
- System DesignReal-time analytics pipeline: day 79 lab
- System DesignDesign a data mesh architecture
- System DesignDesign a data observability system
- ReviewWeekly review and interview recall
- Exercise
- Extend the real-time analytics pipeline with a tested, replay-safe step and record the result.
- Interview question
- How would you design a production data platform for Design a data mesh architecture, including scale, failure handling and trade-offs?
- Outcome
- You can explain Design a data mesh architecture, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 12
Day 80/ 90
Design a unified batch + streaming (Lambda/Kappa)
Plan progress, day 800 of 90 days- SQLJoin algorithms (hash, merge, nested loop)
- DSAMin Cost to Connect All Points
- DSASwim in Rising Water
- DE ConceptsRetries and failure recovery
- System DesignDesign a unified batch + streaming (Lambda/Kappa)
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Design a unified batch + streaming (Lambda/Kappa) and keep a short note of the result.
- Interview question
- How would you design a production data platform for Design a unified batch + streaming (Lambda/Kappa), including scale, failure handling and trade-offs?
- Outcome
- You can explain Design a unified batch + streaming (Lambda/Kappa), complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 12
Day 81/ 90
Design a feature store
Plan progress, day 810 of 90 days- SQLStatistics & the optimizer
- DSAClimbing Stairs
- DSAMin Cost Climbing Stairs
- DE ConceptsPipeline observability
- System DesignDesign a feature store
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Design a feature store and keep a short note of the result.
- Interview question
- How would you design a production data platform for Design a feature store, including scale, failure handling and trade-offs?
- Outcome
- You can explain Design a feature store, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 12
Day 82/ 90
Design a cost-optimized warehouse strategy
Plan progress, day 820 of 90 days- SQLCardinality estimation
- DSAHouse Robber
- DSAHouse Robber II
- DE ConceptsLate data and backfills
- System DesignDesign a cost-optimized warehouse strategy
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Design a cost-optimized warehouse strategy and keep a short note of the result.
- Interview question
- How would you design a production data platform for Design a cost-optimized warehouse strategy, including scale, failure handling and trade-offs?
- Outcome
- You can explain Design a cost-optimized warehouse strategy, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 12
Day 83/ 90
Design a self-serve analytics platform
Plan progress, day 830 of 90 days- SQLCTE materialization trade-offs
- DSADecode Ways
- DSACoin Change
- DE ConceptsStorage layers and raw landing
- System DesignDesign a self-serve analytics platform
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Design a self-serve analytics platform and keep a short note of the result.
- Interview question
- How would you design a production data platform for Design a self-serve analytics platform, including scale, failure handling and trade-offs?
- Outcome
- You can explain Design a self-serve analytics platform, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 12
Day 84/ 90
Design a schema registry & contract system
Plan progress, day 840 of 90 days- SQLSpilling & memory management
- DSAWord Break
- DSALongest Increasing Subsequence
- DE ConceptsPython API pagination
- System DesignDesign a schema registry & contract system
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Design a schema registry & contract system and keep a short note of the result.
- Interview question
- How would you design a production data platform for Design a schema registry & contract system, including scale, failure handling and trade-offs?
- Outcome
- You can explain Design a schema registry & contract system, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Week 13Finish the project demo, résumé and portfolio; complete final mocks and a focused revision plan.
Daily focusWeek 13
Day 85/ 90
Design a financial reconciliation pipeline
Plan progress, day 850 of 90 days- SQLWindow function performance tuning
- SQLInventory Turnover case study
- DSABest Time to Buy/Sell with Cooldown
- DSAPartition Equal Subset Sum
- DSACoin Change II
- DSATarget Sum
- DE ConceptsData normalization trade-offs
- System DesignRecord the final project demo and walkthrough
- System DesignDesign a financial reconciliation pipeline
- System DesignDesign a data catalog & lineage system
- ReviewWeekly review and interview recall
- Exercise
- Record a short demo showing the pipeline, its data quality checks and one replay-safe run.
- Interview question
- How would you design a production data platform for Design a financial reconciliation pipeline, including scale, failure handling and trade-offs?
- Outcome
- You can explain Design a financial reconciliation pipeline, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 13
Day 86/ 90
Design a near-zero downtime migration
Plan progress, day 860 of 90 days- SQLHandling skew in aggregations
- SQLEmployee Hierarchy case study
- DSA0 - 1 Knapsack Problem
- DSASubset Sum Problem
- DSACount Subsets with Sum
- DSAPartition Into 2 Subsets with Min Sum Diff
- DE ConceptsLake, warehouse and lakehouse
- System DesignPolish the resume, portfolio and project README
- System DesignDesign a near-zero downtime migration
- System DesignDesign a GDPR/PII compliant pipeline
- ReviewWeekly review and interview recall
- Exercise
- Write three résumé bullets and a portfolio README that describe the project and its trade-offs.
- Interview question
- How would you design a production data platform for Design a near-zero downtime migration, including scale, failure handling and trade-offs?
- Outcome
- You can explain Design a near-zero downtime migration, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 13
Day 87/ 90
Design a financial reconciliation pipeline
Plan progress, day 870 of 90 days- SQLApproximate distinct (HLL)
- DSALongest Palindromic Substring
- DSAPalindromic Substrings
- DE ConceptsData modeling methods
- System DesignDesign a financial reconciliation pipeline
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Design a financial reconciliation pipeline and keep a short note of the result.
- Interview question
- How would you design a production data platform for Design a financial reconciliation pipeline, including scale, failure handling and trade-offs?
- Outcome
- You can explain Design a financial reconciliation pipeline, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 13
Day 88/ 90
Design a data SLA & freshness monitoring system
Plan progress, day 880 of 90 days- SQLIsolation levels (ACID)
- DSAUnique Paths
- DSALongest Common Subsequence
- DE ConceptsSecure data access and PII
- System DesignDesign a data SLA & freshness monitoring system
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Design a data SLA & freshness monitoring system and keep a short note of the result.
- Interview question
- How would you design a production data platform for Design a data SLA & freshness monitoring system, including scale, failure handling and trade-offs?
- Outcome
- You can explain Design a data SLA & freshness monitoring system, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 13
Day 89/ 90
Design a data quality framework
Plan progress, day 890 of 90 days- SQLDeadlocks & locking
- DSAInterleaving String
- DSAEdit Distance
- DE ConceptsReplay-safe event processing
- System DesignDesign a data quality framework
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Design a data quality framework and keep a short note of the result.
- Interview question
- How would you design a production data platform for Design a data quality framework, including scale, failure handling and trade-offs?
- Outcome
- You can explain Design a data quality framework, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Daily focusWeek 13
Day 90/ 90
Design a batch ingestion framework
Plan progress, day 900 of 90 days- SQLMVCC concepts
- DSABurst Balloons
- DSARegular Expression Matching
- DE ConceptsCost and freshness trade-offs
- System DesignDesign a batch ingestion framework
- ReviewRecall yesterday's and last week's topics; answer one question aloud
- Exercise
- Complete a hands-on exercise for Design a batch ingestion framework and keep a short note of the result.
- Interview question
- How would you design a production data platform for Design a batch ingestion framework, including scale, failure handling and trade-offs?
- Outcome
- You can explain Design a batch ingestion framework, complete today's SQL and DSA practice, and show the result of the hands-on exercise.
Finish the project demo, resume and portfolio; complete final mocks and a focused revision plan.