Request validation is the process of checking incoming data to your API to make sure it is safe, correct, and follows the expected format. This helps protect your system from harmful or accidental mistakes, such as missing required information or malicious input. By validating requests, you prevent attackers from sending dangerous data that could cause security problems or disrupt your service. Learning how to validate requests is a key step in building secure and reliable APIs.

How API Gateways Validate Requests

API Gateways act as the first line of defense for your backend services. When a client sends a request, the gateway checks if the request is well-formed and safe before passing it to your application. This process is called request validation.

Request validation usually involves these checks:

• Making sure the request uses the correct HTTP method, such as GET or POST;
• Confirming all required fields are present in the request body or parameters;
• Checking if the data in each field is in the correct format, like numbers, emails, or dates;
• Rejecting requests with unexpected or extra fields that could be harmful.

Simple example:

Suppose your API expects a login request with a JSON body like this:

{
  "username": "user123",
  "password": "mypassword"
}

The API Gateway will:

• Check that both username and password are included;
• Make sure username is a string and not empty;
• Make sure password is a string and meets length requirements;
• Reject any request with missing fields or extra fields, such as role or admin.

By performing these checks, the API Gateway stops invalid or unsafe requests before they reach your application, protecting your system from common attacks and mistakes.