Unique ID generator

How this question breaks down

1. 1RequirementsCore16 minBefore picking a generator, decide what an ID must promise. It must never collide. It must fit a size budget. It may need to sort by time. It should need no coordination to mint. And it should not leak what it counts.
2. 2SnowflakeCore21 minPack a millisecond timestamp, a machine number and a per-millisecond counter into 64 bits, and every server can mint sortable IDs alone, as long as clocks and machine numbers behave.
3. 3UUIDs and rangesCore22 minTwo ways to mint IDs on many machines at once. Draw 122 random bits and rely on the odds, or keep one counter that hands out blocks of numbers, so it is asked only once per block.

Work through the parts in order and you’ve covered the full design. Each part is one topic.