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

SeniorPrefer not to say
Apr 2026

Summary

Microsoft system design round focused entirely on API lifecycle management. One long question, very structured expectations, felt more like a staff-level design review than a typical SWE screen.

Questions Asked (1)

Q1

Walk through the full end-to-end process for shipping a change to a public-facing API, covering compatibility analysis, versioning strategy, deprecation planning, staged rollout, testing, monitoring, rollback, and customer communication. How does the process differ for breaking versus non-breaking changes?

API & IntegrationsSystem DesignTechnical Trade-offs
Author's notes

This was the whole interview basically.

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AI HintsAI Generated

Suggested Approach

Structure your answer around the API lifecycle, emphasizing the distinction between breaking and non-breaking changes at each stage. Use a concrete example to illustrate the process, and highlight how Microsoft's customer-centric approach influences decisions like versioning and deprecation. Conclude by summarizing key trade-offs and lessons learned.

Pro tip: Emphasize that non-breaking changes can often be shipped continuously with feature flags and canary releases, while breaking changes require a formal deprecation policy with clear timelines and migration support. Mention that at Microsoft, we often use API versioning in the URL or header, and we provide SDKs and tooling to ease migration.

1. Compatibility Analysis

Assess whether the change is breaking or non-breaking by analyzing the API contract, consumer usage, and potential impact. Use tools like OpenAPI diff and telemetry to identify affected clients.

2. Versioning and Deprecation Strategy

For breaking changes, introduce a new API version (e.g., /v2) and deprecate the old one with a clear timeline. For non-breaking changes, add to the existing version, possibly behind a feature flag.

3. Staged Rollout and Testing

Roll out gradually using canary releases and ring deployments, monitoring key metrics. Conduct thorough testing including unit, integration, and contract tests, plus load testing.

4. Monitoring and Rollback

Set up real-time monitoring for errors, latency, and usage patterns. Define rollback criteria and automate rollback if issues arise.

5. Customer Communication

For breaking changes, proactively communicate via multiple channels (blog, email, docs) well in advance, offering migration guides and support. For non-breaking changes, document in release notes.

Key Points to Mention

  • Breaking vs non-breaking changes: definition and examples (e.g., removing a field vs adding an optional field).
  • Versioning strategies: URL path, query parameter, header, or media type versioning; trade-offs.
  • Deprecation policy: timeline, sunset period, and communication plan.
  • Staged rollout techniques: canary releases, feature flags, blue-green deployments.
  • Monitoring and observability: metrics, logs, traces, and alerting for API health.
  • Rollback strategies: automated rollback, version rollback, and data migration considerations.

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