← Back to Directory

OpenAI interview notes, page 9 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 coding question for a Software Engineer role at OpenAI that was more about careful bookkeeping than clever algorithms. The problem looked simple at first glance but the out-of-order timestamps and tie-breaking rules made it trickier than expected.
  • Design a GPU credit ledger class that supports adding credits, charging credits, and querying the balance at any given timestamp. Events can arrive out of order, and the balance at a given time must reflect all events up to that timestamp processed in chronological order, with charges only succeeding if the balance is sufficient at the time they're processed.

“The out-of-order timestamp part is what got me initially.”

View Post

OpenAI·Backend Engineer·Onsite - System Design / Architecture

Apr 2026
System design round at OpenAI for a backend engineer role, focused entirely on building a cloud-based remote dev environment service from scratch. Pretty broad scope for a single session and I felt like I was juggling too many subsystems at once.
  • Design a system that provisions on-demand remote development environments in the cloud. Walk through the full lifecycle: creating, starting, stopping, and destroying a devbox, and cover compute, storage, networking, IDE access, multi-tenant isolation, autoscaling, and cost controls.

“This one sprawled fast.”

View Post

OpenAI·Software Engineer·Onsite - System Design / Architecture

Apr 2026
System design round at OpenAI for a software engineer role. The core problem was building an in-memory social network with snapshot support, which sounds manageable until you get into the versioning rabbit hole.
  • Design an in-memory social network that supports adding users, adding and removing friendships, and retrieving a user's friends. Then extend it to support snapshots: a snapshot() call that captures the current state of the graph, and a getFriendsAt(userId, snapshotId) that returns a user's friends as of that snapshot. Walk through your data representation choices and the time/space trade-offs of different snapshotting strategies.

“I started with the adjacency map part, which felt fine.”

View Post

OpenAI·Software Engineer·Onsite - System Design / Architecture

Apr 2026
Did a system design round at OpenAI for a software engineer role. The interviewer kept pushing for clear component ownership and a well-defined workflow, which I wasn't fully prepared to prioritize over the scaling and fault-tolerance stuff I'd drilled on.
  • Design a payment system.

“I went in ready to talk about replication, failover, all the scaling patterns I'd been studying.”

View Post

OpenAI·Software Engineer·Technical Phone Screen

Apr 2026
OpenAI SWE interview with an ML coding problem around active learning and classifier training. The original post was pretty sparse on details so a lot had to be inferred, but the core task involved building a pipeline to select unlabeled samples for human annotation and then training a classifier on the results.
  • Design and implement a workflow that selects unlabeled samples for human annotation, trains a classifier on the newly labeled data, and outputs evaluation results.

“The problem statement they gave me was weirdly vague.”

View Post

OpenAI·Software Engineer·Technical Phone Screen

Apr 2026
Interviewed for a Research Engineer role at OpenAI and got a coding question about implementing undo/redo on a text buffer. Pretty classic systems design meets data structures territory, but the constraints made it more interesting than it sounds.
  • You have a text buffer with insert, delete, and get_text operations. Add undo and redo support such that every insert/delete is reversible, redo clears when a new operation comes in, and all four operations stay efficient.

“The core insight is storing the inverse of each operation on a stack rather than snapshotting the whole buffer each time.”

View Post

OpenAI·Machine Learning Engineer·Onsite - System Design / Architecture

Apr 2026
System design round at OpenAI for an ML Engineer role, centered entirely on one big open-ended problem about handling uncertainty in a ChatGPT-style assistant. No small warmup questions, just straight into the deep end for the full session.
  • Design a system for a ChatGPT-like assistant that gracefully handles situations where the model doesn't know the answer or can't answer reliably. Cover the architecture, how the system decides what to do (answer, clarify, retrieve, or refuse), and how you'd measure whether it's working.

“This one is deceptively large.”

View Post

OpenAI·Software Engineer·Onsite - System Design / Architecture

Apr 2026
Did a system design round at OpenAI for a software engineer role, got asked to design a video scheduling service along the lines of Sora. Pretty intense scope for one session.
  • Design a video scheduling service similar to Sora. Walk through the architecture, key components, and how you'd handle scale.

“This one is deceptively wide.”

View Post

OpenAI·Machine Learning Engineer·Onsite - System Design / Architecture

Apr 2026
System design round at OpenAI for an ML Engineer role, focused entirely on building a search autocomplete system end to end. Pretty demanding scope for a single session, covering everything from data pipelines to abuse prevention.
  • Design a search autocomplete system that returns query suggestions in real time as a user types, with sub-100ms latency per keystroke, personalization, trending query support, typo tolerance, multilingual support, and abuse/privacy safeguards.

“This is a beast of a question and I underestimated how many dimensions they actually wanted covered.”

View Post

OpenAI·Software Engineer·Technical Phone Screen

Apr 2026
Phone screen for a software engineer role at OpenAI. One coding question, crossword-style word placement problem. Short round, nothing else to report.
  • Solve a crossword or word placement problem, where you need to fit words into a grid according to certain constraints.

“Apparently this comes up a lot in OpenAI screens.”

View Post