.tip

Postgres 18 ships uuidv7() in core. It is a UUID with a timestamp prefix, so inserts land at the right edge of the index like an integer would, and you keep the part of UUIDs that mattered: generating keys anywhere, no collisions on merge.

id uuid PRIMARY KEY DEFAULT uuidv7()

For an existing v4 table, swapping the default is enough. New pages pack tightly from then on, and a REINDEX CONCURRENTLY later tidies the rest.