Split-brain primary divergence
You run a 3-node self-managed PostgreSQL cluster with a custom Patroni-style failover. At 02:14 customers report some writes 'disappearing' on refresh. Dashboards: two nodes (A and B) both report themselves as primary; A is in us-east-1a, B in us-east-1c; the etcd DCS shows intermittent connectivity between AZs starting 02:09; both A and B are accepting writes and each has a different, diverging WAL position. A network team is mid-incident on an inter-AZ link. How do you 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 45 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.