| 1 | How should Airflow retries and idempotency work together? | Airflow | Medium | conceptual, scenario | |
| 2 | ETL vs ELT: what factors decide the choice? | Data Engineering | Easy | conceptual, architecture | |
| 3 | Data lake vs warehouse vs lakehouse: when would you choose each? | Data Engineering | Medium | conceptual, architecture | |
| 4 | How would you design an idempotent batch pipeline? | Data Engineering | Medium | architecture, scenario | |
| 5 | How would you investigate a suddenly slower data pipeline? | Data Engineering | Medium | debugging, scenario | |
| 6 | What are the most important data-quality checks in production? | Data Engineering | Medium | conceptual, scenario | |
| 7 | How would you design a CDC pipeline? | Data Engineering | Hard | architecture, scenario | |
| 8 | What is Unity Catalog used for? | Databricks | Easy | conceptual | |
| 9 | What problems does Delta Lake solve? | Delta Lake | Easy | conceptual | |
| 10 | What is schema evolution and when is it safe? | Delta Lake | Medium | conceptual, scenario | |
| 11 | Binary Search: Find a Target in a Sorted Array in O(log n) | DSA | Easy | coding | |
| 12 | Contains Duplicate: Detect Whether Any Value Appears Twice | DSA | Easy | coding | |
| 13 | Invert Binary Tree: Recursive and Iterative Mirror Solutions | DSA | Easy | coding | |
| 14 | Linked List Cycle: Floyd's Fast and Slow Pointers | DSA | Easy | coding | |
| 15 | Majority Element: Find the Value That Fills More Than Half the Array | DSA | Easy | coding | |
| 16 | Maximum Depth of Binary Tree: Recursive DFS, Iterative DFS and BFS | DSA | Easy | coding | |
| 17 | Merge Two Sorted Lists: Dummy Head Iteration and Recursion | DSA | Easy | coding | |
| 18 | Move Zeroes: Shift Zeros to the End While Keeping Order | DSA | Easy | coding | |
| 19 | Reverse Linked List: Iterative and Recursive Solutions | DSA | Easy | coding | |
| 20 | Two Sum: Find Two Indices That Add Up to a Target | DSA | Easy | coding | |
| 21 | Valid Anagram: Check Whether Two Strings Use the Same Letters | DSA | Easy | coding | |
| 22 | Valid Palindrome: Check a Phrase While Ignoring Case and Punctuation | DSA | Easy | coding | |
| 23 | 3Sum: Find All Unique Triplets That Sum to Zero | DSA | Medium | coding | |
| 24 | Add Two Numbers: Digit-by-Digit Addition on Linked Lists | DSA | Medium | coding | |
| 25 | Clone Graph: Deep-Copy a Connected Graph with a Hash Map and BFS or DFS | DSA | Medium | coding | |
| 26 | Combination Sum II: Use Each Value Once and Avoid Duplicate Answers | DSA | Medium | coding | |
| 27 | Combination Sum: Reach a Target with Reusable Values via Backtracking | DSA | Medium | coding | |
| 28 | Container With Most Water: Maximise Area Between Two Lines | DSA | Medium | coding | |
| 29 | Copy List with Random Pointer: Hash Map and Interleaving Solutions | DSA | Medium | coding | |
| 30 | Course Schedule II: Return a Valid Course Order with Topological Sort | DSA | Medium | coding | |
| 31 | Course Schedule: Detect a Cycle in a Prerequisite Graph with Kahn's Algorithm | DSA | Medium | coding | |
| 32 | Encode and Decode Strings: Serialise a List of Strings Safely | DSA | Medium | coding | |
| 33 | Find First and Last Position of a Value: Lower and Upper Bound Binary Search | DSA | Medium | coding | |
| 34 | Find Minimum in Rotated Sorted Array: Binary Search Against the Right End | DSA | Medium | coding | |
| 35 | Find the Duplicate Number: Cycle Detection on an Array | DSA | Medium | coding | |
| 36 | Graph Valid Tree: Check Edge Count, Connectivity and Cycles with Union-Find | DSA | Medium | coding | |
| 37 | Group Anagrams: Bucket Words That Share the Same Letters | DSA | Medium | coding | |
| 38 | Insert Interval: Add a Range to a Sorted List and Merge Overlaps | DSA | Medium | coding | |
| 39 | Koko Eating Bananas: Binary Search on the Answer | DSA | Medium | coding | |
| 40 | Letter Combinations of a Phone Number: Cartesian Product by Backtracking | DSA | Medium | coding | |
| 41 | Longest Consecutive Sequence: Longest Run of Consecutive Integers in O(n) | DSA | Medium | coding | |
| 42 | LRU Cache: Hash Map Plus Doubly Linked List for O(1) Operations | DSA | Medium | coding, architecture | |
| 43 | Max Area of Island: Largest Connected Land Region with Flood Fill | DSA | Medium | coding | |
| 44 | Maximum Subarray: Largest Sum of a Contiguous Slice with Kadane's Algorithm | DSA | Medium | coding | |
| 45 | Merge Intervals: Combine Every Overlapping Range | DSA | Medium | coding | |
| 46 | Non-overlapping Intervals: Fewest Removals to Eliminate Overlaps | DSA | Medium | coding | |
| 47 | Number of Connected Components in an Undirected Graph with Union-Find | DSA | Medium | coding | |
| 48 | Number of Islands: Count Connected Land Cells with BFS, DFS or Union-Find | DSA | Medium | coding | |
| 49 | Pacific Atlantic Water Flow: Reverse Multi-Source BFS from Both Oceans | DSA | Medium | coding | |
| 50 | Palindrome Partitioning: Split a String into Palindromes by Backtracking | DSA | Medium | coding | |
| 51 | Permutations: Every Ordering of Distinct Values with Backtracking | DSA | Medium | coding | |
| 52 | Product of Array Except Self: Prefix and Suffix Products Without Division | DSA | Medium | coding | |
| 53 | Redundant Connection: Find the Edge That Closes a Cycle with Union-Find | DSA | Medium | coding | |
| 54 | Remove Nth Node From End of List: One Pass with a Gap of n | DSA | Medium | coding | |
| 55 | Reorder List: Find the Middle, Reverse, Then Interleave | DSA | Medium | coding | |
| 56 | Rotate Image: Turn a Square Matrix 90 Degrees Clockwise in Place | DSA | Medium | coding | |
| 57 | Rotting Oranges: Minutes to Spread via Level-by-Level Multi-Source BFS | DSA | Medium | coding | |
| 58 | Search a 2D Matrix: Binary Search over a Flattened Sorted Grid | DSA | Medium | coding | |
| 59 | Search in Rotated Sorted Array: One-Pass Binary Search | DSA | Medium | coding | |
| 60 | Set Matrix Zeroes: Zero Out Rows and Columns in Place | DSA | Medium | coding | |
| 61 | Sort Colors: One-Pass Three-Way Partition of 0s, 1s and 2s | DSA | Medium | coding | |
| 62 | Spiral Matrix: Read a Grid in Clockwise Spiral Order | DSA | Medium | coding | |
| 63 | Subarray Sum Equals K: Count Contiguous Slices With a Given Sum | DSA | Medium | coding | |
| 64 | Subsets II: Power Set Without Duplicates When Values Repeat | DSA | Medium | coding | |
| 65 | Subsets: Generate the Power Set with Include/Exclude Backtracking | DSA | Medium | coding | |
| 66 | Surrounded Regions: Capture Enclosed Cells by Flood-Filling from the Border | DSA | Medium | coding | |
| 67 | Time Based Key-Value Store: Versioned Lookups with Binary Search | DSA | Medium | coding, architecture | |
| 68 | Top K Frequent Elements: Return the k Most Common Values | DSA | Medium | coding | |
| 69 | Two Sum II: Find a Pair With a Target Sum in a Sorted Array | DSA | Medium | coding | |
| 70 | Valid Sudoku: Check Rows, Columns and Boxes for Repeated Digits | DSA | Medium | coding | |
| 71 | Word Search: Trace a Word Through a Letter Grid with DFS Backtracking | DSA | Medium | coding | |
| 72 | Median of Two Sorted Arrays: Partition Binary Search in O(log min(m, n)) | DSA | Hard | coding | |
| 73 | Merge k Sorted Lists: Min-Heap and Divide-and-Conquer Solutions | DSA | Hard | coding | |
| 74 | N-Queens: Place Non-Attacking Queens Row by Row with Backtracking | DSA | Hard | coding | |
| 75 | Reverse Nodes in k-Group: In-Place Group Reversal on a Linked List | DSA | Hard | coding | |
| 76 | Trapping Rain Water: Total Water Held Between Elevation Bars | DSA | Hard | coding | |
| 77 | Word Search II: Find Many Words in a Grid with a Trie and Backtracking | DSA | Hard | coding | |
| 78 | Explain Kafka partitions and consumer groups. | Kafka | Medium | conceptual, architecture | |
| 79 | What is at-least-once delivery and what problems can it create? | Kafka | Medium | conceptual, scenario | |
| 80 | When should you avoid Python UDFs in PySpark? | PySpark | Medium | conceptual, optimization | |
| 81 | When would you use a broadcast join in Spark? | PySpark | Medium | conceptual, optimization | |
| 82 | Explain shallow copy vs deep copy. | Python | Easy | conceptual, debugging | |
| 83 | List vs tuple vs set: when would you use each in a data pipeline? | Python | Easy | conceptual | |
| 84 | What is a generator and why can it help with large datasets? | Python | Easy | conceptual, coding | |
| 85 | How should exceptions be handled in production data pipelines? | Python | Medium | conceptual, scenario | |
| 86 | What are Snowflake virtual warehouses? | Snowflake | Easy | conceptual | |
| 87 | How do micro-partitions affect Snowflake query performance? | Snowflake | Medium | conceptual, optimization | |
| 88 | What is the difference between a transformation and an action in Spark? | Apache Spark | Easy | conceptual | |
| 89 | Explain Spark jobs, stages and tasks. | Apache Spark | Medium | conceptual | |
| 90 | How does partition count affect Spark performance? | Apache Spark | Medium | optimization, conceptual | |
| 91 | What causes a shuffle in Spark? | Apache Spark | Medium | conceptual | |
| 92 | What is data skew and how can you mitigate it? | Apache Spark | Hard | optimization, debugging | |
| 93 | Explain INNER JOIN vs LEFT JOIN with a practical example. | SQL | Easy | conceptual, coding | |
| 94 | How do window functions differ from GROUP BY? | SQL | Easy | conceptual, coding | |
| 95 | Customer Lifetime Value: SQL Case Study with 8 Approaches | SQL | Medium | coding, optimization, scenario | |
| 96 | Daily Active Users: SQL Case Study with 8 Approaches | SQL | Medium | coding, optimization, scenario | |
| 97 | Find the second-highest salary without using a simple MAX approach. | SQL | Medium | coding | |
| 98 | How would you detect and remove duplicate records safely? | SQL | Medium | coding, scenario | |
| 99 | How would you optimize a slow analytical SQL query? | SQL | Hard | optimization, scenario | |
| 100 | Monthly Revenue: SQL Case Study with 8 Approaches | SQL | Hard | coding, optimization, scenario | |