A Go implementation of ULID, a lexicographically sortable identifier alternative to UUID.
oklog/ulid is a Go implementation of the ULID specification, providing a library and command-line tool for generating and parsing Universally Unique Lexicographically Sortable Identifiers. It creates identifiers that combine timestamp-based ordering with randomness in a compact, URL-safe format, offering a more efficient and database-friendly alternative to traditional UUIDs.
Go developers building distributed systems, databases, or applications requiring time-ordered unique identifiers, such as those working on logging, event sourcing, or data indexing.
Developers choose this library for its lexicographic sortability, compact encoding, and flexibility in entropy source selection, allowing performance, security, and concurrency trade-offs tailored to specific use cases.
Universally Unique Lexicographically Sortable Identifier (ULID) in Go
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ULIDs are naturally ordered by generation time due to their embedded timestamp, making them ideal for database indexing and chronological sorting without additional columns, as highlighted in the specification.
Uses Crockford's Base32 to encode 128 bits into 26 URL-safe characters, which is shorter than UUID's 36 characters, optimizing storage and readability.
Provides optional monotonic entropy to ensure IDs generated within the same millisecond are ordered, useful for high-concurrency applications, though with implementation caveats.
Allows developers to choose entropy sources via io.Reader, enabling trade-offs for security, performance, or concurrency, as demonstrated in the advanced usage examples.
Includes a CLI utility for generating and parsing ULIDs from the terminal, aiding in debugging, scripting, and quick operations without writing Go code.
Requires developers to provide their own entropy sources, which can be confusing for newcomers and error-prone, as the README admits it's 'a bit confusing' and warns about concurrency and security issues.
Monotonic entropy has limitations, such as requiring careful synchronization and performance trade-offs, adding complexity to ensure correct ordering within milliseconds.
Does not default to cryptographically secure entropy; users must manually configure sources like crypto/rand for security-sensitive cases, increasing setup effort compared to libraries with built-in security.
As a Go port, it is unsuitable for projects in other languages, limiting its use in polyglot environments where consistent ID generation across multiple platforms is needed.