KUIDs

KUIDs are a class of globally unique identifiers used to label entities such as resources, users, devices, and events across distributed systems. The term does not have a single universal standard; implementations are domain- and organization-specific. KUIDs are designed to be unique across space and time, support efficient storage and comparisons, and facilitate merging and tracing in multi-service architectures.

Conventional characteristics of KUIDs include a namespace or prefix that identifies the project or domain and a unique suffix that encodes time and/or randomness. Encodings vary, with common formats including hexadecimal, base32, or base64 strings. Some KUID schemes are lexicographically sortable by time, while others prioritize compactness or readability.

Generation methods for KUIDs vary. Time-based schemes combine a timestamp with a random component, providing ordering and uniqueness; cryptographic randomness offers strong collision resistance; deterministic, name-based schemes may derive a KUID from a stable input such as a resource name and namespace. Notable related schemes in practice include ULID and KSUID, which share design goals and trade-offs.

Usage and considerations for KUIDs include identifying resources across services, supporting deduplication, auditing, and cross-system joins, and serving as traceable identifiers in event logs. When choosing a KUID approach, organizations consider collision resistance, privacy implications, readability, and interoperability with existing systems. Privacy-conscious implementations avoid embedding meaningful data in the identifier itself and favor opaque components.

See also: UUID, ULID, KSUID.