Paytm Technical Lead Interview Experience Feb 2026 (Rejected)

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 👇

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🧠 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

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🔹 Question 1: LRU Cache

• Classic design problem (similar to LeetCode 146)
• Expected O(1) get and put
• 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 LinkedHashMap directly
• Real-world use cases (caching, DB optimization)

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🔹 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)

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💬 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

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🎯 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

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🚀 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)

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Happy to discuss more if anyone is preparing for similar roles 🙌