AdvancedSystem-Design
45 min
Design an API Gateway / Edge Layer
APIsNetworkingSecurityCachingReliability
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Interview Question
Design a multi-tenant API gateway that handles routing, auth, rate limiting, request/response transformations, canarying, and observability across regions.
Key Points to Cover
- Request lifecycle: TLS termination, authn/z, routing, transforms
- Policy control plane vs data plane separation; hot reload of rules
- Rate limiting/quotas per tenant and endpoint; burst handling
- Resilience: circuit breaking, retries, timeouts, hedging
- Multi-region routing (Geo/DNS/Anycast) and canary/blue-green
- Observability: structured logs, distributed tracing, per-route SLOs
Evaluation Rubric
Clear request lifecycle & components25% weight
Sound control/data plane separation25% weight
Robust resilience & rollout strategy25% weight
Strong observability & SLO thinking25% weight
Hints
- 💡Consider Envoy/NGINX at the edge with a declarative control plane.
Common Pitfalls to Avoid
- ⚠️Single point of failure for the gateway itself.
- ⚠️Inefficient or unscalable rate limiting implementation.
- ⚠️Lack of granular tenant isolation in policies and configuration.
- ⚠️Inadequate observability leading to blind spots in performance or security.
- ⚠️Complex and brittle request/response transformation logic that is difficult to manage.
Potential Follow-up Questions
- ❓How do you do multi-tenant isolation?
- ❓How would you ship breaking header transforms safely?
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