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Stripe·Software Engineer·Technical Phone Screen·Senior

SeniorPrefer not to say
Jun 2026Remote

Summary

Stripe system design screen for a software engineer role, focused on designing a server health-tracking system from scratch. The problem built up incrementally, starting with the SET HEALTHY operation, and felt more like a distributed systems contract negotiation than a typical coding round.

Questions Asked (1)

Q1

You're building a server health-tracking system. Servers are pre-registered with an id and metadata. Design and define the SET HEALTHY operation: what arguments does it take, what happens if the server was never registered, how do repeated calls behave, and how does it handle overwriting prior status?

System DesignAPI & IntegrationsData Modeling
Author's notes

I jumped straight into the happy path and forgot to define the error contract for unregistered servers until the interviewer nudged me.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the operation's contract: its arguments, return values, and error semantics. Then walk through the edge cases—unregistered server, repeated calls, and overwriting prior status—and justify your choices with idempotency and data consistency in mind.

Pro tip: Explicitly state that SET HEALTHY should be idempotent and discuss how you'd handle concurrent updates (e.g., using a version or timestamp) to avoid lost updates, showing you think about real-world reliability.

1. Define the operation signature

Specify the arguments (e.g., server_id, optional timestamp/version) and return type (e.g., success/failure, updated status). Consider whether metadata is needed.

2. Handle unregistered servers

Decide on behavior: return an error (e.g., 404 Not Found) or auto-register? Justify based on system requirements and data integrity.

3. Ensure idempotency for repeated calls

Explain that calling SET HEALTHY multiple times should have the same effect as one call, and discuss how to achieve this (e.g., no side effects beyond setting status).

4. Manage overwriting prior status

Describe how to update the status field, including handling concurrent updates (e.g., optimistic locking) and preserving history if needed.

5. Summarize with trade-offs

Briefly recap your design choices and mention any trade-offs (e.g., strict validation vs. flexibility) to show balanced thinking.

Key Points to Mention

  • Idempotency: repeated calls should not change the outcome or cause errors.
  • Error handling for unregistered servers: return a clear error (e.g., 404) rather than silently creating a server.
  • Concurrency control: use versioning or timestamps to prevent lost updates when multiple clients set health status.
  • Data model: store health status as a field on the server record, possibly with a last_updated timestamp.
  • API design: consider RESTful semantics (e.g., PUT /servers/{id}/health) and appropriate status codes.
  • Observability: log status changes for auditing and debugging.

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