Answer
PostgreSQL stores multiple row versions with transaction IDs. Readers check tuple visibility using snapshots, avoiding locks. Writers create new versions instead of overwriting data. VACUUM later removes dead tuples.
Quick Answer
MVCC in PostgreSQL works by storing multiple versions of each row. Each tuple has xmin (XID of creating transaction) and xmax (XID of deleting/updating transaction). A transaction can see a tuple if xmin is committed and precedes its snapshot, and xmax is either 0 or from a transaction that started after the snapshot. No locks needed for reads - the snapshot determines visibility mathematically.
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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