Paytm Technical Lead Interview Experience Feb 2026 (Rejected)
Summary
I had an interesting and well-structured coding round with Paytm for a Technical Lead role. The interview primarily focused on core Data Structures & Algorithms, problem-solving approaches, clean code, and discussions around real-world applications.
Full Experience
I had an interesting and well-structured coding round with Paytm for a Technical Lead role. Sharing a quick summary that might help others preparing 👇
🧠 Round Focus
The interview was a mix of:
- Core DSA fundamentals
- Problem-solving approach
- Clean code + explanation
- Some discussion around real-world usage of problems
🔹 Question 1: LRU Cache
- Classic design problem (similar to LeetCode 146)
- Expected O(1)
getandput - Key focus areas:
- Combining HashMap + Doubly Linked List
- Handling edge cases like updates & eviction
- Writing clean, modular code
👉 Follow-up discussion:
- Thread safety considerations
- Why not use
LinkedHashMapdirectly - Real-world use cases (caching, DB optimization)
🔹 Question 2: Course Schedule
- Graph-based problem (LeetCode 207)
- Detect if all courses can be completed
👉 Approach:
- Modeled as Directed Graph
- Solved using DFS cycle detection (Topological sort concept)
👉 Follow-ups:
- BFS (Kahn’s Algorithm) alternative
- How to return course order (Course Schedule II)
- Real-world analogy (task dependencies, job scheduling)
💬 Discussion Highlights
- Interviewer focused more on thought process than just code
- Asked about trade-offs, optimizations, and edge cases
- Some behavioral questions around:
- Transition to Technical Lead
- Ownership & system design thinking
🎯 Key Takeaways
- Be very clear with fundamentals (HashMap, Graphs, Linked List)
- Always explain:
- Why this approach?
- Time & Space complexity
- Think beyond code → real-world systems & scalability
- Communication matters as much as correctness
🚀 Final Tip
If you're targeting Paytm (or similar product companies), prepare:
- LRU Cache, LFU Cache
- Graph problems (cycle detection, topological sort)
- System design basics (caching, async processing, idempotency)
Happy to discuss more if anyone is preparing for similar roles 🙌
Interview Questions (2)
LRU Cache Design
I was asked to design a data structure that follows the constraints of a Least Recently Used (LRU) cache. I needed to implement the get and put operations, both expected to run in O(1) average time complexity. Key focus areas included combining HashMap + Doubly Linked List, handling edge cases like updates & eviction, and writing clean, modular code.
Follow-up discussion included: Thread safety considerations, why not use LinkedHashMap directly, and real-world use cases (caching, DB optimization).
Course Schedule - Cycle Detection
Given the total number of courses I had to take and a list of prerequisite pairs, I was asked to determine if I could finish all courses. In other words, detect if it's possible to complete all courses given their prerequisites (similar to LeetCode 207).