Webhook delivery with ordering
Design the delivery engine for outbound webhooks where per-endpoint event ORDER matters (e.g. invoice.created must reach the customer before invoice.paid) and customer endpoints are flaky. 200M events/day, ~80k destination endpoints. You need at-least-once delivery, strict per-resource ordering, retries with backoff that don't reorder, and a way for slow endpoints not to block everyone. Focus on the ordering + retry guarantees, not the public API.
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.
Clarify5:00 left
Estimate5:00 planned
Design15:00 planned
Deep dive12:00 planned
Failure8:00 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.