PhonePe - interview guide

PhonePe interview questions - a complete guide

At PhonePe, both machine coding and DSA are reported to be eliminating rounds. Here is how to prepare for both, with UPI as the context.

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About PhonePe

PhonePe is a large Indian digital payments app, especially for UPI payments. Its engineering roles deal with problems of large scale, reliability and fast transactions.

This guide covers 13 PhonePe interview questions with answers - what each question checks and how to answer it - plus the PhonePe interview process, round by round, a 7-day preparation plan for freshers, tips and the mistakes to avoid.

PhonePe hiring process

  1. Machine coding

    Sometimes ~2 hours live, sometimes take-home - modular code, in-memory storage and test cases.

  2. DSA

    Medium to medium-hard - graphs, stacks, sets; discussion of complexity.

  3. Design and hiring manager

    Low-level/system design, depth on your resume, CS basics and behavioural.

PhonePe doesn't publish its process. This information mostly comes from experienced candidates' reports - the fresher process can differ. Confirm with the recruiter.

Sources (checked 16 October 2026): PhonePe Careers. Hiring processes change - read the official notice before you apply.

PhonePe interview questions and answers

Machine coding and design

  1. 1.Machine coding: build a vehicle rental service.

    What they're checking
    Reported - OOP, modular code and tests.
    How to answer
    Branch, Vehicle (type), Booking. Add a branch/vehicle, book (a time slot), show available vehicles. An in-memory store, a separate service layer, and some test cases. Spend the first 15 minutes clarifying requirements.

  2. 2.Explain the UPI payment flow at a high level.

    What they're checking
    Understanding the domain.
    How to answer
    User app → their bank/PSP → NPCI (the switch) → the receiver's bank → confirmation back. Status and failure handling at every step.

  3. 3.How would you prevent a double debit in a payment app?

    What they're checking
    Reliability.
    How to answer
    A unique transaction ID, idempotent processing, and status reconciliation - so a retry doesn't charge twice.

DSA

  1. 4.Find the largest rectangle in a histogram.

    What they're checking
    A stack - medium-hard.
    How to answer
    Indices on a monotonic stack; when a shorter bar comes, pop and compute the area. O(n).

  2. 5.How many separate groups (connected components) are there?

    What they're checking
    Union-Find / DFS.
    How to answer
    Join with Union-Find or count with DFS; use path compression in Union-Find.

  3. 6.Longest consecutive sequence (in an unsorted array).

    What they're checking
    A smart use of a hash set.
    How to answer
    Build a set; only start counting from a number whose (x-1) isn't in the set; count upwards. O(n).

SQL, Linux and hiring manager

  1. 7.SQL: count each user's transactions per day.

    What they're checking
    Practical understanding of data.
    How to answer
    COUNT(*) with GROUP BY user_id, DATE(created_at).

  2. 8.How would you see which process is using the most CPU/memory on Linux?

    What they're checking
    Production debugging.
    How to answer
    top or htop; ps aux --sort=-%mem; and tail -f for log files.

  3. 9.Describe one design decision in your project and its trade-off.

    What they're checking
    The depth of your thinking.
    How to answer
    What you chose, what the alternative was, and why - such as SQL vs NoSQL.

More questions

  1. 10.How would you implement a daily transaction limit?

    What they're checking
    A payments business rule.
    How to answer
    Keep a running total per user per day (in a cache/DB); check it when a new transaction comes, with an atomic update.

  2. 11.Detect a cycle in an undirected graph.

    What they're checking
    Graphs.
    How to answer
    In DFS, finding a visited node other than the parent means a cycle; or the same parent in Union-Find.

  3. 12.Where would you put a cache in a read-heavy system?

    What they're checking
    Design thinking.
    How to answer
    For data read again and again (like merchant details) - with a TTL and invalidation on update.

  4. 13.What if the requirements in machine coding are unclear?

    What they're checking
    Process.
    How to answer
    Spend the first 10-15 minutes asking questions, write down assumptions, and confirm them with the interviewer.

7-day preparation plan for the PhonePe interview

  1. Day 1: One machine coding problem in 2 hours (rental/parking).
  2. Day 2: Stack problems - histogram, next greater.
  3. Day 3: Graphs - Union-Find, BFS/DFS.
  4. Day 4: A second machine coding problem, with tests.
  5. Day 5: SQL and Linux commands.
  6. Day 6: The UPI/payments flow and your project's trade-offs.
  7. Day 7: A mock DSA round and revision.

Preparation tips

  • In machine coding, clarify requirements first, then the core flow, then tests.
  • Keep code modular - one job per class.
  • Have SQL and basic Linux commands ready too.
  • Every round is reported to be eliminating - treat each one as the final.

Mistakes to avoid

  • Starting to code in machine coding without clarifying requirements.
  • Writing everything in one big class - modularity matters.
  • Not saving time for tests.

Frequently asked questions

What is the PhonePe machine coding round like?

Reports mention sometimes ~2 hours live, sometimes take-home - with emphasis on modular code and test cases.

How hard is PhonePe's DSA?

Commonly medium to medium-hard - graphs, stacks, sets.

Does PhonePe ask about SQL and Linux?

SQL and Linux questions have featured prominently in some reports.

Is the PhonePe process the same for freshers?

Most reports are from experienced hires - confirm the fresher process with the recruiter.

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