PostgreSQL MVCC: Table Bloat Does Not Cause Read Amplification, Here's Why

A common misconception holds that PostgreSQL's MVCC mechanism causes reads to slow down as dead row versions accumulate before VACUUM runs, but this is inaccurate. Sequential scans examine heap tuples directly and skip invisible ones, while index scans follow version chains only within a single page, limiting overhead. PostgreSQL also performs lightweight garbage collection during normal reads through hint bits and opportunistic heap pruning, even when autovacuum is disabled. Index scans mark dead entries as LP_DEAD after a single visibility check, preventing repeated heap lookups in future queries. As a result, while space amplification (bloat) is a real concern in PostgreSQL, read performance does not degrade proportionally as dead tuples build up.