Openai·Software Engineer·Technical Phone Screen·Senior

SeniorPrefer not to say

May 2026

Summary

Interviewed for a full-stack role at OpenAI and got a system design question about building a multi-bot chat dispatcher. Pretty interesting problem, more software architecture than pure algorithms, which I wasn't fully expecting.

Questions Asked (1)

Design and implement a chat system with multiple bots (e.g. one that responds to keywords, one that books meetings, one that auto-replies for away users). Incoming messages should be dispatched to all registered bots, each bot can return zero or more responses, and adding new bots later should be straightforward.

System DesignTechnical Trade-offsAPI & Integrations

Author's notes

My first instinct was to just write a big if-else block and I'm glad I caught myself before saying that out loud.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and scale, then propose a modular architecture with a central dispatcher and a bot interface, emphasizing extensibility and fault isolation. Walk through the message flow, discuss trade-offs (sync vs async, ordering, error handling), and outline how to add new bots without modifying core logic.

Pro tip: Show maturity by discussing how to handle bot failures gracefully—e.g., timeouts, circuit breakers, and dead-letter queues—so one misbehaving bot doesn't break the entire chat system.

1. Clarify Requirements and Scale

Ask about expected message volume, latency requirements, bot response time limits, and whether responses should be aggregated or sent individually. This sets the stage for design decisions.

2. Define Bot Interface and Dispatcher

Design a common interface (e.g., `handleMessage(message) -> List<Response>`) that all bots implement. The dispatcher receives incoming messages and invokes all registered bots, collecting their responses.

3. Design Message Flow and Concurrency

Decide whether to process bots synchronously or asynchronously. For scalability, use a thread pool or async calls with timeouts. Ensure responses are aggregated and sent back to the user in order.

4. Handle Failures and Isolation

Implement error handling per bot: catch exceptions, set timeouts, and use circuit breakers. Log failures and optionally retry or dead-letter. This prevents one bot from affecting others.

5. Extensibility and Registration

Allow dynamic registration of bots via a registry (e.g., config file, service discovery). New bots just implement the interface and register; no changes to dispatcher code.

Key Points to Mention

Bot interface with a standard method signature for handling messages and returning responses.
Dispatcher pattern to route messages to all registered bots and collect responses.
Asynchronous processing with timeouts to avoid blocking and improve scalability.
Fault isolation: per-bot error handling, circuit breakers, and logging.
Dynamic bot registration via a registry or plugin system for easy extensibility.
Trade-offs: synchronous vs asynchronous, ordering of responses, and idempotency.

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.