GetUserById

GetUserById is a function used to retrieve a user record by its unique identifier. It is commonly found in backend services, APIs, and data access layers. The function accepts a single parameter representing the user's identifier and returns a user object or null/None if no such user exists. It may also raise an error for invalid input or if the underlying data store is unavailable.

Common language forms include JavaScript or TypeScript, where getUserById(id) is typically asynchronous and returns a Promise that resolves to a User object or null; Python, where get_user_by_id(user_id) returns an Optional[User]; Java, which might define Optional<User> getUserById(String id); and C#, where GetUserByIdAsync(string id) might return Task<User?>.

The function usually queries a data source such as a relational database, document store, or in-memory cache, relying on an index on the user identifier to enable fast lookups. The returned user object generally contains non-sensitive user fields, and implementations may redact or omit password hashes or other secret data when returning results to callers.

Error handling and edge cases include validating input types and formats, in which case an invalid id may cause an immediate error; returning null/None or Optional.empty when no matching user exists; and propagating or translating data-store errors when the backend is unavailable or the query fails.

Performance considerations include ensuring the identifier column is indexed, considering caching for frequently accessed users, and avoiding unnecessary full-table scans. See also related functions such as getUserByEmail, listUsers, createUser, updateUser, and deleteUser.

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