Core conceptsintermediate
Lock manager (heavyweight locks)
The subsystem that grants and queues table- and object-level locks, tracking what each transaction holds and what it waits for.
What this means
The part of Postgres that hands out locks on whole tables and objects, and keeps track of who holds what and who's waiting in line. When two transactions want the same object, this is the traffic cop deciding who gets it now and who queues behind them.
Why it matters operationally
Every blocking incident, lock timeout, and deadlock is ultimately a story told by the lock manager's wait queues.