Answer
Snapshot-too-old occurs when required row versions are vacuumed. Fix by avoiding long-running transactions, tuning autovacuum aggressively, running analytics on replicas, and monitoring vacuum lag via system views.
Quick Answer
Snapshot-too-old error (PostgreSQL 9.6+): when old_snapshot_threshold is set and a query's snapshot is too old to reconstruct MVCC visibility, it fails. Caused by long-running queries combined with high data churn. Fix: reduce long-running transaction duration, increase old_snapshot_threshold (careful: uses more memory), or restructure analytics queries to run faster. Monitor with pg_stat_activity for long snapshots.
S
SugharaIQ Editorial Team
Verified Answer
This answer has been peer-reviewed by industry experts holding senior engineering roles to ensure technical accuracy and relevance for modern interview standards.
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Source: SugharaIQ