← Back to all experiencesProcess Overview
- Two weeks from start to finish.
Interview Rounds Breakdown
Recruiter Screen20 mins
BehavioralMotivation
The round focused on the candidate's interest in infrastructure work.
The discussion centered on the candidate's motivation for joining OpenAI.
Questions Asked
Why OpenAI and what kind of infrastructure work are you interested in?Behavioral
Take Home Assignment48 hours
System DesignCodingTesting
The task involved building a Webhook Delivery System with endpoint registration, event delivery, retries, and dead-letter queues.
The candidate utilized Python, FastAPI, and SQLite.
Technical Deep Dive60 mins
Code ReviewSystem DesignDebugging
The candidate walked through architectural decisions made during the take-home assignment.
The interviewer requested live extensions, specifically HMAC signature verification and event type filtering.
System Design60 mins
System DesignDatabase Internals
The candidate was tasked with designing an in-memory database supporting basic SQL operations.
The candidate opted for a column-oriented storage approach.
The interviewer pushed for optimization of JOIN operations, moving from nested loop joins to hash or sort-merge joins.
The discussion evolved into implementing ACID guarantees using Write-Ahead Logging (WAL) and Multi-Version Concurrency Control (MVCC).
Behavioral
BehavioralLeadership
The interview covered topics including technical disagreements, failed projects, and prioritization.
The candidate provided an example of pushing back on a technical decision due to ethical concerns regarding excessive user data logging.
Questions Asked
Describe a time you pushed back on a technical decision for ethical reasons.
Key Takeaways & Advice
Candidate Advice
- Do not rush the take-home assignment, as it is a critical component for advancing to the onsite.
- Acknowledge that system design rounds are excellent opportunities to identify personal knowledge gaps.
- Focus on gaining production-level distributed database experience to improve performance in system design interviews.
Final Verdict
The candidate was unfortunately rejected.
Emphasis was placed on clean code and testing over feature completeness.
The implementation included a worker process for polling, exponential backoff, and a circuit breaker mechanism.
Questions Asked
Build a Webhook Delivery System with retries and dead-letter queues.System DesignBackend
A critical bug regarding worker crashes and stuck events was identified.
The candidate and interviewer collaboratively designed a lease-based approach to handle event requeuing.
Questions Asked
Extend the webhook system with HMAC signature verification and event type filtering.SecurityBackend
The interviewer consistently probed deeper into every architectural decision, testing the limits of the candidate's knowledge.
Questions Asked
Design an in-memory database with support for CREATE, INSERT, SELECT, and JOIN operations.System DesignDatabases