emqx/doc/uuid.md

Mongodb ObjectId

• 4-byte value representing the seconds since the Unix epoch,
• 3-byte machine identifier,
• 2-byte process id, and
• 3-byte counter, starting with a random value.

Flake Id

• 64bits Timestamp
• 48bits WorkerId
• 16bits Sequence

emqttd Id

• 64bits Timestamp: erlang:now(), erlang:system_time
• 48bits (node+pid): Node + Pid -> Integer
• 16bits Sequence: PktId