API gateway cascading failures
Design a reverse proxy / API gateway sitting in front of ~300 internal microservices handling 1M req/s. It must pool upstream connections, apply per-route timeouts and retries, and shed load when a downstream is slow without taking down the whole gateway. A single slow dependency currently causes the whole gateway to run out of threads. Explain the architecture and how you prevent one bad backend from cascading.
What a strong answer looks like
Clarify scale and constraints first. Propose a clean component breakdown, then go deep on the hard parts (data model, bottlenecks, consistency, failure modes) and name the trade-offs you are making.
Clarify4:30 left
Estimate4:30 planned
Design13:30 planned
Deep dive10:30 planned
Failure7:00 planned
Which questions mattered is sealed until you submit. Telling you now would just be handing over the edge cases.
Run or narrate your approach, then ask the coach.