Mid Backend at OpenAI

BackendMidWithdrew◆ Commonly asked· 2025

Mid backend interview. Coding-heavy early, design and behavioral later.

The loop · 5 rounds

Round 01 · 3 questions

DSA / Coding

Data structures & algorithms on a whiteboard or shared editor.

Merge intervals.
MidMedium◆ Commonly asked
#intervals#sorting
PracticeLeetCode GeeksforGeeks
Meeting rooms II — minimum rooms required.
MidMedium◆ Commonly asked
#heap#intervals
PracticeLeetCode GeeksforGeeks
Rotting oranges.
MidMedium◆ Commonly asked
#bfs#grid
PracticeLeetCode GeeksforGeeks

Round 02 · 2 questions

Machine Coding

Build a working component or service under time pressure.

Build an in-memory rate limiter as a middleware.
MidMedium◆ Commonly asked
#rate-limit#middleware
PracticeGeeksforGeeks Search
Implement an idempotent "charge" endpoint.
MidHard◆ Commonly asked
#idempotency#payments
PracticeGeeksforGeeks Search

Round 03 · 1 question

Low-Level Design

Object-oriented / low-level design of a focused module.

Design an in-memory file system.
MidHard◆ Commonly asked
#oop#trees
PracticeGeeksforGeeks Search

Round 04 · 3 questions

Tech Deep-Dive

Deep questions on your core stack and fundamentals.

Explain database replication lag and how to mitigate it.
MidMedium◆ Commonly asked
#databases#replication
PracticeGeeksforGeeks Search
How do you secure secrets and handle auth tokens?
MidMedium◆ Commonly asked
#security
PracticeGeeksforGeeks Search
Explain eventual consistency with a real example.
MidHard◆ Commonly asked
#distributed
PracticeGeeksforGeeks Search

Round 05 · 2 questions

Behavioral / HR

Values, collaboration, and past-experience (STAR) questions.

Tell me about the hardest bug you have debugged.
Mid◆ Commonly asked
#debugging#star
Tell me about a time you went above and beyond for a customer.
Mid◆ Commonly asked
#customer#star

◆ This experience is composed from commonly reported questions for this role and level. Real, individually-shared interviews will be layered in over time.