PostgreSQL data volume fills overnight
A primary PostgreSQL instance's data volume fills to 100% at 04:00 and the database refuses writes (it shuts down to protect itself). Disk dashboards show steady growth on pg_wal/ over the last 12 hours specifically — table data size is flat. A read replica went offline for maintenance at 16:00 yesterday and never reconnected, and a logical replication slot for a downstream analytics CDC pipeline shows a replication-lag/slot-retained-bytes metric climbing all night. Normal table churn is unchanged. Triage and recover.
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.