vacuum_failsafe_age

The emergency brake, added in Postgres 14. When a table’s age crosses vacuum_failsafe_age (default 1.6B) during a vacuum, that vacuum abandons everything optional (cost-based throttling off, index cleanup skipped, truncation skipped) and does nothing but freeze as fast as the hardware allows. It is the difference between a wraparound near-miss and a shutdown; you are not supposed to see it fire, and if you do, the freeze settings upstream were wrong.