Metric label cardinality explosion
A service's RSS grows ~80MB/hour and it gets OOMKilled every ~30 hours; restart resets it. Heap profiles show the memory is dominated by one in-process map keyed by a metric *label* derived from a request attribute — and the number of distinct keys grows without bound. The growth rate jumped sharply two days ago when a client started sending a unique request ID into a header that the service (incorrectly) uses as a metric label dimension, so every request creates a new label series that's retained forever. Request rate is flat. Triage and mitigate.
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 35 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.