API Gateway
Auth, routing, and caching for every partner call — thin, but in front of everything.
Keep partner APIs answering through a launch-day flood while a gateway box dies and the backend slows.
The gateway tier does auth, routing and response caching for every partner call — it's thin, but it's in front of everything. A well-tuned response cache means most calls never reach the backend at all; a thin gateway fleet means one dead box drowns the survivors.
Components in play
- Edge LB — Spreads partner traffic across the gateway fleet.
- API gateway — Auth, rate headers, routing — every call passes through here.
- Response cache — Serves repeated GET responses without touching the backend.
- Backend services — The actual business logic behind the gateway.
- Records DB — Durable state the backend reads and writes.
Graded on these SLOs
- ≥ 99.00%Calls succeed
- ≤ 90 msResponse p99
- ≥ 12k rpsCarry the launch
- ≤ 90%Gateway headroom
- ≤ 10Lean footprint
The brief
Design the API gateway that fronts every partner integration: auth, rate limiting, routing, and response caching before a request ever reaches a backend service. A launch-day flood can triple traffic in minutes, and because the gateway sits in front of everything, one under-provisioned tier here takes down every partner at once.
Functional
- Authenticate and route partner calls to the right backend service
- Cache repeatable GET responses
- Apply per-partner rate limits
Non-functional
- Must absorb sudden multi-x traffic spikes (launches, retries)
- High availability — every partner integration depends on this one tier
- Backend services should only see the traffic the cache can't answer
Warm-up: design decisions
Optional theory to prime the calls a senior engineer would make before you build.
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