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> contention slowdowns caused by having a primary key that needs a lock (incrementing key)

This kind of problem only exists in unsophisticated databases like SQLite. Postgres reserves whole ranges of IDs at once so there is never any contention for the next ID in a serial sequence.

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I think you’re thinking out the cache property of a sequence, but it defaults to 1 (not generating ranges at once). However, Postgres only needs a lightweight lock on the sequence object, since it’s separate from the table itself.

MySQL does need a special kind of table-level lock for its auto-incrementing values, but it has fairly sophisticated logic as of 8.0 as to when and how that lock is taken. IME, you’ll probably hit some other bottleneck before you experience auto-inc lock contention.

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