← Back to Directory

OpenAI interview notes, page 18 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·Frontend Engineer·Onsite - System Design / Architecture

May 2026
System design round at OpenAI for a frontend engineer role. The question was about designing the ChatGPT Playground and I thought I handled it fine, but looking back I think I was too passive the whole time and that probably cost me.
  • Design the ChatGPT Playground, covering the parameter controls, preset configurations, and both frontend and backend architecture.

“I answered everything they asked, including failure handling for server and model outages.”

View Post

OpenAI·Software Engineer·Onsite - System Design / Architecture

May 2026
OpenAI software engineer onsite, system design round focused on building a payment abstraction layer sitting between users and upstream processors like Amex. Pretty standard fintech design problem but the scope was broader than I expected.
  • Design a payment system that sits as an intermediary layer between users and upstream payment processors (e.g. Amex).

“The core challenge was scoping it right.”

View Post

OpenAI·Software Engineer·Onsite - Coding / Algorithms

May 2026
Got a coding round at OpenAI for a software engineer role and the problem was a consistent hashing ring with virtual nodes. Definitely not a LeetCode easy. The problem statement was dense and I spent probably the first ten minutes just re-reading it.
  • Implement a consistent hashing ring with virtual nodes that supports adding and removing shards, and routes keys to the nearest clockwise virtual node using a custom 32-bit FNV-1a hash function.

“The problem had a lot of moving parts and I kept second-guessing myself on the tie-breaking rule.”

View Post

OpenAI·Software Engineer·Onsite - Behavioral / Leadership

May 2026
Behavioral round at OpenAI for a software engineer role. Pretty standard set of questions but they were clearly trying to connect each one back to your specific background, so generic answers probably don't land well here.
  • Tell me about yourself and the most impactful project you've worked on.
  • Describe a time you had a conflict with a teammate or manager. How did you handle it?
  • Walk me through a project that failed or didn't hit its goal. What did you take away from it?
  • Why do you want to work at this company and specifically on this team?
  • How do you manage ambiguity or sudden shifts in priorities?

“I structured it as situation-action-result and it felt fine, but in hindsight I probably spent too long on context and rushed the actual impact part.”

View Post

OpenAI·Software Engineer·Onsite - System Design / Architecture

May 2026
Did a system design round for a Research Scientist role at OpenAI focused entirely on ML experiment infrastructure. The problem was meaty and I felt like I was playing catch-up for most of it.
  • Design and implement a flexible configuration system for ML experiments that supports declarative experiment definitions and multiple parameter sweep strategies like grid search, random search, and sequential sweeps.
  • How would you handle experiment versioning and reproducibility in this system? What needs to be tracked and how do you ensure a run can be exactly reproduced later?
  • How would this configuration system integrate with the actual training pipeline? Walk through the handoff from config definition to a running training job.

“I jumped straight into the sweep mechanics and forgot to anchor on the config schema first.”

View Post

OpenAI·Software Engineer·Onsite - System Design / Architecture

May 2026
Architecture round at OpenAI for a Software Engineer role, centered on designing an Online Chess system. Spent most of the time on the matching service and ran out of steam before covering everything.
  • Design an Online Chess system.
  • How would the matching service consume a widened bucket queue?

“Went deep on the matching service early and kind of got stuck there.”

View Post

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

May 2026
Did a system design round for an ML Engineer role at OpenAI, focused on version control for systems. Not a ton of detail to share but it was a legitimate design round, not a coding screen.
  • Design a version control system for machine learning models and related system artifacts.

“The content here is pretty sparse so I'm going off the round type.”

View Post

OpenAI·Software Engineer·Onsite - System Design / Architecture

May 2026
System design round at OpenAI for a software engineer role, focused entirely on designing a chatbot service from scratch. The scope was broader than I expected, covering everything from streaming to safety pipelines, and I felt like I was playing catch-up the whole time.
  • Design a chatbot service that supports multi-turn conversations, multiple concurrent conversations per user, streaming responses, and persisted conversation history.
  • How would you handle context window limits as conversations grow longer, and what tradeoffs exist between truncation, summarization, and retrieval-based approaches?
  • Walk through how you'd architect the LLM inference layer to support high throughput with dynamic batching and KV-cache reuse for streaming.
  • What does your safety pipeline look like, covering input moderation, output moderation, jailbreak detection, and PII redaction?
  • How would you approach observability for this system, including cost tracking, latency monitoring, and supporting A/B tests for prompt or model changes?

“This is the kind of question where you think you know where to start and then realize you have no idea how deep it goes.”

View Post

OpenAI·Software Engineer·Technical Phone Screen

May 2026
Interviewed for a software engineering role at OpenAI and got a problem that looked deceptively simple on the surface. Build a tiny in-memory database, one table, strings only. Spent most of the time on the SELECT sorting logic which has more edge cases than you'd expect.
  • Implement a simple in-memory database supporting SET, GET, and SELECT commands on a single table where all values are strings. SELECT must filter rows by a column value and sort results by another column lexicographically, with tie-breaking by row key.

“The SET and GET parts took maybe five minutes.”

View Post

OpenAI·Software Engineer·Onsite - System Design / Architecture

May 2026
System design round at OpenAI for a SWE role, focused entirely on building a webhook delivery system at massive scale. The interview went deep on failure handling and retry logic, which I was not fully prepared for.
  • Design a webhook delivery system that handles 1 billion events per day with at-least-once delivery guarantees, retry logic, and failure isolation.
  • How would you design the REST API for registering webhooks and querying delivery history, including filtering and pagination?
  • Walk me through your database schema for storing webhooks and delivery records. How do you enforce the one-event-per-user constraint and handle sharding at scale?
  • What would you cache in this system and how would you handle cache invalidation when a webhook is updated or deleted?
  • How would you implement retry logic for failed webhook deliveries, including backoff strategy, distinguishing error types, and preventing one slow subscriber from blocking others?
  • How do you prevent SSRF attacks when making outbound HTTP requests to user-supplied callback URLs, and how would you implement payload signing for subscribers?

“I started with the API surface and database schema which felt safe, but the interviewer kept pushing toward the delivery pipeline.”

View Post