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OpenAI interview notes, page 13 of 67

Mid-sized

Most of these OpenAI write-ups come from Software Engineers (460), then Machine Learning Engineers (137) and Backend Engineers (23). The most reported rounds are the technical phone screen (335), the system design round (229), the onsite coding round (32) and the behavioral / leadership round (22).

667 interview notes · updated Jul 2026

OpenAI·Software Engineer·Technical Phone Screen

Apr 2026
Got a distributed systems coding problem at OpenAI that was way more involved than I expected for what I thought would be a straightforward interview. The core question was about async message passing across a network of nodes, and it kept growing with follow-ups that I was not fully prepared for.
  • You're given the root node of a distributed network where nodes can only communicate via an async sendAsyncMessage API. Implement the receiveMessage handler so the system can discover the full network and count all nodes, starting from the root.
  • Instead of returning just a count, output the full network topology as a nested string, like 1(2(4,5),3(6)).
  • How would you handle node crashes or dropped messages in this system? Walk through retries, duplicate responses, idempotency, request IDs, and caching.
  • If multiple traversal requests hit the same node concurrently, how do you isolate per-request state and handle thread safety?
  • Implement sendAsyncMessage locally for testing purposes and write tests that exercise the full async counting flow end to end.

“The setup took me a minute to absorb.”

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OpenAI·Software Engineer·Technical Phone Screen

Apr 2026
OpenAI SWE coding round centered entirely on a credit ledger system they call GPU Credit, with a keyed-grant variant that adds out-of-order event handling. You get six test cases upfront and that's basically your rubric for the whole session.
  • Design a credit ledger system with three operations: issue a credit grant with an amount and expiration, consume credit (draining earliest-expiring grants first, possibly spanning multiple grants), and query the balance at a given point in time.
  • Extend the ledger so each grant has a unique ID and a relative expiration, and handle out-of-order event arrival: a subtract operation might be submitted before the grant it needs to draw from has been registered.
  • What happens to get_balance when the replayed credit goes negative due to an over-burn? Should it return 0, None, or raise an error?

“The core of the whole interview.”

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OpenAI·Software Engineer·Technical Phone Screen

Apr 2026
Code reading round at OpenAI for a SWE role. You get a 400-line PyTorch file and have to work through three parts plus a bonus, with complexity questions sprinkled throughout on the existing code, not just whatever you write.
  • What is the time and space complexity of a matrix multiplication operation A @ B in this codebase?
  • Given this unfamiliar 400-line PyTorch file, walk us through the data flow and explain what the code is doing.

“This sounds like a warmup but it isn't.”

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OpenAI·Software Engineer·Onsite - Coding / Algorithms

Apr 2026
OpenAI SWE interview, 75-minute coding round centered on building a toy language interpreter from scratch. The live extension twist mid-round is real and not just a rumor, so be ready for the goalposts to move.
  • Implement a small interpreter for a toy programming language: tokenize source input, parse statements (assignments, arithmetic expressions, print/output), evaluate them, and handle any language extensions the interviewer adds mid-round.

“This is the whole round, not just one question.”

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OpenAI·Backend Engineer·Onsite - System Design / Architecture

Apr 2026
System design round at OpenAI for a backend engineer role. The whole thing was focused on designing a CI/CD platform from scratch, think GitHub Actions or Jenkins, and they wanted you to go deep on basically every layer of the stack.
  • Design a CI/CD platform similar to GitHub Actions or Jenkins. Walk through how you'd handle build triggers, user-defined pipelines, isolated job execution, log streaming, artifact storage, deploy approvals, scheduling across thousands of concurrent builds, secrets management, and sandboxing for long-running jobs.

“This is a massive question and I think I underestimated the scope for the first few minutes.”

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OpenAI·Software Engineer·Onsite - System Design / Architecture

Apr 2026
OpenAI system design round that was heavier than I expected. The prompt came with a multi-page requirements doc plus screenshots and an animation, so you're not just whiteboarding vague boxes. You have to cover the full stack but the frontend is the anchor.
  • Given a requirements document and a visual demo, walk through the full frontend architecture: framework choice, routing, component breakdown, state management, data fetching approach, error and loading states, accessibility, performance optimizations, and testing strategy.
  • Define the API contract for this application. What endpoints do you expose, what do the request and response schemas look like, how do you handle pagination and auth, and how does each UI state map back to a specific API call?
  • Design the backend to support this application. Cover service boundaries, data modeling, storage choices, caching, background jobs, idempotency, observability, and how the system scales.
  • How would you deploy this application? Describe your CI/CD pipeline, environment configuration, and your approach to canary releases and rollbacks.
  • Walk through one critical user flow end to end, describing every UI action and the corresponding API calls in sequence. Also explain how you'd validate your design against the demo, scope under time pressure, and handle ambiguous requirements.

“This is where I spent most of my time and still felt like I was leaving things out.”

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OpenAI·Software Engineer·Technical Phone Screen

Apr 2026
Technical round at OpenAI for a software engineer role. The format was pretty standard: pick a past project and walk through it. They wanted something cross-functional and high-impact, which I had, but the depth of follow-up still caught me working.
  • Walk me through a past project that was cross-functional and had significant impact.

“I'd prepped a project that touched multiple teams so I wasn't scrambling for material.”

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OpenAI·Software Engineer·Recruiter / HR Screen

Apr 2026
Screened for a software engineer role at OpenAI. Just one question from what was shared, but it's the kind that trips people up if they haven't actually thought it through.
  • Why do you want to work at OpenAI specifically, and how do your skills connect to the team you're interviewing for?

“This looks easy until you realize 'I think AI is cool' isn't going to cut it.”

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OpenAI·Software Engineer·Technical Phone Screen

Apr 2026
OpenAI coding round where they had me build a working interpreter from scratch for a toy language. Starts simple but they keep adding requirements, so the initial design really matters.
  • Build an interpreter for a small toy programming language that supports variable assignment, arithmetic, and print output, with the expectation that follow-up rounds will add features like conditionals, loops, and functions.

“The part that tripped me up wasn't parsing, it was scope.”

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OpenAI·Software Engineer·Take-home Assignment

Apr 2026
Take-home assignment for an iOS Engineer role at OpenAI. You get a sample Xcode project with a README and have to fill in the missing functionality, with an emphasis on UI work. SwiftUI is the preferred path but UIKit is fine too.
  • Given a provided Xcode project and README, implement the missing UI functionality using either UIKit or SwiftUI, following clean architecture principles with proper view, view model, and state management separation.

“SwiftUI being 'preferred' is the kind of thing you notice after you've already committed to UIKit.”

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