Distributed tracing pipeline
Design a distributed tracing pipeline for a microservice platform of ~800 services producing 5M traces/min, average 40 spans/trace (so ~200M spans/min at peak). The business wants to keep essentially all error traces and all traces slower than the p99 latency for that endpoint, but can afford to store only ~2% of the healthy traces. Storage budget allows ~30 days hot. Design ingest, the sampling decision, and trace storage/retrieval by trace ID and by service+latency+error filters.
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.