Coordinator bottleneck on scale
Your distributed query engine scales workers horizontally and normally near-linearly. After onboarding a large analytics customer you added 3x more worker nodes to handle their load, but total throughput barely improved and per-query latency got worse. Worker CPU is moderate. Tracing shows every query, on start and on each stage transition, calls a single central coordinator/metadata service to fetch the schema and assign splits — and that coordinator is now at 100% CPU with a growing request queue. How do you triage, and what's the real fix?
What a strong answer looks like
Stop the bleeding first (mitigate), then form hypotheses from real signals. Separate root cause from symptom, communicate status as you go, and close with what prevents a repeat.
0:00 of about 30 min
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.