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Question
Postgres primary. Disk usage on the data volume climbed steadily over 2 days and just hit 100%; the DB is now refusing writes / crashing on `could not write to file ... No space left on device`. The `pg_wal` directory is huge. There was no traffic spike. Two weeks ago a team set up a logical-replication subscriber for a new data pipeline; that subscriber has been down for days. Triage, get writes back safely, 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.
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