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Stripe·Software Engineer·Onsite - System Design / Architecture·Senior

Senior
May 2026

Summary

Stripe system design round focused on building out a server health-tracking system from scratch. The REGISTER operation was the starting point, and the whole thing hinged on getting the data model and contract right before anything else could work.

Questions Asked (1)

Q1

Design and implement a REGISTER operation for a server health-tracking system. Define what arguments it accepts, what it returns on success versus duplicate registration, and how the stored data supports future operations like status updates and queries.

System DesignData ModelingAPI & Integrations
Author's notes

The duplicate case is where I stumbled a bit.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and constraints, then define a clear API contract for the REGISTER operation, including arguments, success and duplicate responses. Design the data model to support future operations like status updates and queries, and discuss trade-offs and edge cases.

Pro tip: Demonstrate idempotency by making REGISTER safe to retry, and discuss how you'd handle concurrent registrations to avoid race conditions. This shows you think about reliability and distributed systems, which is crucial at Stripe.

1. Clarify Requirements

Ask questions to understand the scope: What is a 'server'? What health metrics are tracked? What are the expected scale and consistency requirements? This ensures your design meets actual needs.

2. Define API Contract

Specify the REGISTER operation's arguments (e.g., server ID, hostname, metadata) and return values for success (e.g., 201 Created with server object) and duplicate (e.g., 409 Conflict with existing server details).

3. Design Data Model

Choose a storage schema that supports efficient updates and queries. Consider a key-value store or relational DB with a unique identifier, and include fields for status, timestamps, and metadata.

4. Address Edge Cases

Discuss handling of duplicate registrations (idempotency), concurrent requests, and validation errors. Explain how to ensure data consistency and avoid race conditions.

5. Support Future Operations

Explain how the stored data enables status updates (e.g., by server ID) and queries (e.g., list all servers with a given status). Mention indexing and access patterns.

Key Points to Mention

  • Idempotency: REGISTER should be idempotent so repeated calls with the same server ID don't create duplicates.
  • Unique identifier: Use a stable server ID (e.g., UUID or hostname) as the primary key to ensure uniqueness.
  • Return codes: 201 Created for new registration, 409 Conflict for duplicates, with appropriate response bodies.
  • Data model: Include fields like server_id, hostname, status, created_at, updated_at, and metadata for extensibility.
  • Concurrency: Use database constraints (unique index) or optimistic locking to handle concurrent registrations.
  • Scalability: Consider partitioning or sharding by server ID if the system needs to handle millions of servers.

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