Request Validation

Summary

Checking that incoming request data (body, params, query) matches your expected shape and constraints before your business logic runs — your API's first line of defense.

• 1Add validation to a POST endpoint using a library like Zod, Joi, or express-validator.
• 2Return clear, field-specific error messages when validation fails.
• 3Learn to validate at the API boundary even if your database also has constraints.