PayPay | Japan | June 2025 | Backend Engineer | Interview Experience[Rejected]

paypay logo
paypay
Backend EngineerJapan5 years
June 11, 202512 reads

Summary

I interviewed for a Backend Engineer role at PayPay in Japan in June 2025 and was rejected after several rounds, primarily due to not performing well in the Data Structures and Algorithms (DSA) rounds.

Full Experience

Current Employer: Product based MNC YOE: 5+

Application Process: Recruiter reached out on LinkedIn Interview Process Round 1: Online Assessment on CodeSignal 2 DSA Questions based on array, String, HashMap, Stack Question1: String manipulation with Stack(Easy) Question2: https://leetcode.com/problems/number-of-adjacent-elements-with-the-same-color (Same question with different constraints) Time : 70 mins

Round 2: General tech knowledge Past projects(most challenging) Monolith vs Microservices Sql vs NoSQL ACID properties in detail One scenario based question:- How to handle multiple pay click by user in Payment System(Gave Idempotency key + Rate Limitting based solution) Time : 45 mins

Round 3(Loop): DSA : Sync vs Async Programming(how async wait works internally) Generators in Python JIT compilation in Java(working in depth) SkipList Data structure(working + time complexity of insert, delete) Bloom Filter(how to delete element from BF, told we can't, follow-up:- which DS similar to Bloom Filter supports deletion) Bellman-Ford Algorithm(working and Time Complexity)

One DSA question(Leetcode Hard), working code was expected in 20 mints:- https://leetcode.com/problems/add-edges-to-make-degrees-of-all-nodes-even/ Time : 60 mins

Verdict: Rejected DSA round didn't went well, was not able to answer most of the questions(I mean who will read about Cuckoo Filter(same as Bloom filter with deletion capability)). Also 20 mints for a Leetcode Hard(may be a CM on Codeforces can solve).

One day after the DSA round, I got the rejection mail, no feedback was given as it's against their policy.

Interview Questions (9)

Q1
Number of Adjacent Elements with the Same Color (Modified)
Data Structures & Algorithms

A LeetCode problem (Number of Adjacent Elements with the Same Color) was asked, with different constraints.

Q2
Payment System: Handling Multiple Clicks
System Design

Scenario-based question: How to handle multiple pay clicks by a user in a payment system.

Q3
Sync vs Async Programming Internals
Other

Question on Sync vs Async Programming, specifically how async/await works internally.

Q4
Python Generators
Other

Question on Generators in Python.

Q5
JIT Compilation in Java
Other

Question on JIT compilation in Java, working in depth.

Q6
SkipList Data Structure
Data Structures & Algorithms

Discussion on SkipList Data structure: working and time complexity of insert, delete operations.

Q7
Bloom Filter Deletion and Alternatives
Data Structures & Algorithms

Question on Bloom Filter: how to delete elements from a Bloom Filter. Follow-up: which data structure similar to Bloom Filter supports deletion (e.g., Cuckoo Filter).

Q8
Bellman-Ford Algorithm
Data Structures & Algorithms

Question on Bellman-Ford Algorithm: working and Time Complexity.

Q9
Add Edges to Make Degrees of All Nodes Even
Data Structures & AlgorithmsHard

A LeetCode Hard problem (Add Edges to Make Degrees of All Nodes Even) was given, with working code expected in 20 minutes.

Preparation Tips

Suggestions: Keep resume updated with skills you are well versed with(having Node.Js and Python from my past experience backfired me as there were multiple questions on those skills)

I had mentioned(in my resume) that I've done Competivie programming in past and I think that was the reason he asked me a Leetcode Hard problem(20 mints). Don't mention such thing if you are out of touch from CP

Discussion (0)

Share your thoughts and ask questions

Join the Discussion

Sign in with Google to share your thoughts and ask questions

No comments yet

Be the first to share your thoughts and start the discussion!