Read-your-writes routing lost
Your app writes to a Postgres primary and routes reads to replicas, with a rule: for ~2s after a user writes, route *their* reads to the primary so they see their own change (read-your-writes). After a deploy at 16:00 that moved this routing decision behind a new load balancer, users intermittently report that a setting they just saved 'didn't save' — then it's fine on the next reload. Dashboards: replica lag is normal (~200ms), error rate flat, write success rate 100%. How do you triage, restore read-your-writes, and confirm no writes were actually lost?
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.