findbyid

FindById is a method used in data access libraries to retrieve a single record or document by its unique identifier. It is commonly provided to simplify lookups by the primary key or _id field and is widely used across databases and ORMs.

In MongoDB and related ODMs such as Mongoose, findById(id) searches by the document’s _id and returns the matching document. The operation is generally asynchronous and returns a promise or uses a callback. If no document matches, the result is typically null (or undefined, depending on the API). The id must usually be provided in the correct type, such as an ObjectId, and malformed ids can raise an error.

In relational and other ORM frameworks, the equivalent behavior is offered by methods like findById, findByPk, or find with a primary key predicate. These methods return the entity wrapped in an Optional/Maybe type or null when not found, depending on the framework. The id type can be numeric, UUID, or another primary key type, and lookups are usually served by the primary key index for efficiency.

Return values are typically a single entity or a not-found indicator; some APIs differentiate between not found and error cases. You should consider handling not-found results explicitly and be aware of differences in return types across libraries.

Alternatives include findOne with a predicate on the id field, findByPk, or explicit queries that specify the id condition. The method is most effective for direct primary key lookups and should be used when you expect at most one matching record.