Cache stampede on aligned expiry
At 18:00 exactly, every minute on the minute, your homepage feed service spikes: Redis cache-hit ratio briefly craters, the Postgres origin sees a burst of identical heavy 'trending posts' queries, p99 latency triples for ~10 seconds, then recovers. This started after yesterday's deploy that introduced a 'trending' module cached with a 60-second TTL and a fixed expiry aligned to the wall clock. How do you triage and fix this?
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.