UUIDv7 (RFC 9562, section 5.7): random ids, and record versions that strictly increase on a node.

Bit layout (128 bits, 16 bytes):

   48b unix_ts_ms | 4b ver=7 | 12b rand_a | 2b var=10 | 62b rand_b
  

v7/0 fills rand_a and rand_b with random bits, for ids that need no order. v7_monotonic/1 is the version of a record this node signs (RFC 9562, section 6.2, method 1): rand_a is a counter within the millisecond, reseeded with a random 11-bit value at each new millisecond, and the 60 bits of millisecond and counter are the larger of that fresh prefix and the last one issued plus one. A counter that runs out moves to the next millisecond. So the versions a node issues strictly increase, also across a wall-clock step back.

A version is an order, not a time. A record's created_at stays the wall-clock fact; after a clock step back a version's millisecond field can run ahead of it, and nothing reads that field.

This process owns the table holding the last prefix issued and runs under macula_root. Callers advance it themselves, each version with at most three atomic table operations that only ever raise the row, so no version waits on a message or on another caller. Without the table, between an owner's exit and its restart, and after a restart, the next version starts again from the clock.