I was researching a solution to generate unique IDs and I liked the Twitter snowflake approach. These are my notes about this approach.
What is Twitter’s snowflake approach?
It is a solution to generate unique IDs in distributed systems. Twitter uses this approach in Tweets, DM’s, Lists and etc.
- IDs are unique and sortable
- IDs include time. (ordered by date)
- IDs fit 64-bit unsigned integers.
- Only numerical values.
Sign bit (1 bit): Reserved bit (It is always 0). This can be reserver for future requests. It can be potentially used to make the overall number positive.
Timestamp(41 bit): Epoch timestamp in a millisecond (Snowflake’s default epoch is equal to Nov 04, 2010, 01:42:54 UTC)
Machine ID(10-bit): accommodates 1024 machines
Sequence number(12-bit): It is a local counter per each machine and increments by 1. The number reset to 0 in every millisecond. Theoretically, a machine can support a max of 4096 (2¹²) new IDs per second.
Advantages & Disadvantages of the Twitter Snowflake Approach
- It is 64-bit long, it is half the size of UUIDs
