customid

Customid is a term used in information systems to describe a user-provided or externally supplied identifier that uniquely identifies a resource within a given scope. Unlike system-generated IDs, a customid is created or supplied by the client or an external source and is intended to be stable across operations and datasets.

In application programming interfaces and data integration, a customid serves as an external key that can be used to correlate records across systems. It enables idempotent operations in APIs, where a request that includes a previously seen customid can be mapped to an existing resource rather than creating a duplicate.

In databases and data modeling, a customid may be implemented as a unique key or alternate key. It is often indexed and constrained to be non-null and unique within the relevant table or collection. Depending on the system, a customid may be immutable or allowed to change under controlled circumstances.

Implementation considerations include ensuring global and/or scoped uniqueness, choosing a character set and length, and documenting the semantics to avoid ambiguity. Privacy and security concerns include avoiding exposure of sensitive data in the customid and ensuring proper access control when resolving or mapping external keys.

Common pitfalls include relying on a customid as the sole identifier of a resource when external systems may generate conflicting values, and the complications that arise if external providers reassign or reorganize IDs. Related terms include external_id, natural key, and alternate key.