This is the repository that holds all KSUID for Ruby gems. What is a KSUID, you ask? The original readme for the Go library does a great job of explaining what they are and how you can use them, so we excerpt it here.
KSUID is for K-Sortable Unique IDentifier. It's a way to generate globally unique IDs similar to RFC 4122 UUIDs, but contain a time component so they can be "roughly" sorted by time of creation. The remainder of the KSUID is randomly generated bytes.
Distributed systems often require unique IDs. There are numerous solutions out there for doing this, so why KSUID?
Unlike the more common choice of UUIDv4, KSUIDs contain a timestamp component that allows them to be roughly sorted by generation time. This is obviously not a strong guarantee as it depends on wall clocks, but is still incredibly useful in practice.
Snowflake IDs and derivatives require coordination, which significantly increases the complexity of implementation and creates operations overhead. While RFC 4122 UUIDv1 does have a time component, there aren't enough bytes of randomness to provide strong protections against duplicate ID generation.
KSUIDs use 128-bits of pseudorandom data, which provides a 64-times larger number space than the 122-bits in the well-accepted RFC 4122 UUIDv4 standard. The additional timestamp component drives down the extremely rare chance of duplication to the point of near physical infeasibility, even assuming extreme clock skew (> 24-hours) that would cause other severe anomalies.
The binary and string representations are lexicographically sortable, which allows them to be dropped into systems which do not natively support KSUIDs and retain their k-sortable characteristics.
The string representation is that it is base 62-encoded, so that they can "fit" anywhere alphanumeric strings are accepted.
KSUIDs are 20-bytes: a 32-bit unsigned integer UTC timestamp and a 128-bit randomly generated payload. The timestamp uses big-endian encoding, to allow lexicographic sorting. The timestamp epoch is adjusted to March 5th, 2014, providing over 100 years of useful life starting at UNIX epoch 14e8. The payload uses a cryptographically strong pseudorandom number generator.
The string representation is fixed at 27-characters encoded using a base 62 encoding that also sorts lexicographically.
Currently, there are two gems available:
- KSUID for Ruby provides the main data type and handling for KSUIDs. If you want to use them outside of a database, this will be all you need.
- KSUID for ActiveRecord handles integrating with ActiveRecord. If you're using ActiveRecord and want to serialize KSUID columns, you will want this gem.