1 min lesson
Score against the rubric
Consider this situation: "In your webhook-delivery mock, what's the cleanest way to give consumers an exactly-once experience without claiming exactly-once delivery?" Start with the decision, then the evidence.
Step 1 of 2
Score against the rubricSelf-grade
- Clear abstractions
- Did boundaries between components and the product/infra contract come out crisp or did everything blur into one box?
- Defensible trade-offs
- When you chose at-least-once over exactly-once or SQS over Kafka, did you name the cost you accepted and why it's the right one here?
- Scale awareness
- Did you reason about 1M+ DAU concretely - hot paths, caching, DB scaling, multi-region - or hand-wave it?
- Security
- Did auth, signing, token rotation and least-privilege show up unprompted, given this layer is existential for the product?
Record the run and rewatch it. The thing to check is whether you led with strong, defensible opinions or hedged everything into “it depends.” The JD asks for someone with defensible positions on reliability and performance. A panel of staff engineers can smell a manager who has lost the thread of how the systems actually work and the tell is a design with no opinions in it.
“I'd build webhook delivery as at-least-once, because exactly-once across a network is a fantasy. I push the dedupe responsibility to consumers via idempotency keys, accept that they'll occasionally see a duplicate and spend my reliability budget on getting every event delivered within sixty seconds instead.”