Split-brain write divergence
A network partition briefly isolated your primary Postgres from the HA orchestrator. The orchestrator declared it dead and promoted a standby. Then the partition healed — and now you have a serious mess: some app instances (still able to reach the old node) kept writing to the OLD primary, while others wrote to the newly-promoted one. Both nodes accepted writes for ~90 seconds. Now the two diverge: conflicting rows, broken sequences, duplicate ids. Triage, contain the damage, and prevent recurrence.
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 40 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.