An API Gateway is a natural place to enforce security controls centrally, since it sits in front of every request before it reaches internal microservices.
Key Points: • Authentication verifies the caller's identity, typically by validating an OAuth2/JWT token before allowing the request to proceed. • Authorization checks whether the authenticated caller has permission for the specific resource or action being requested. • SSL/TLS termination encrypts data in transit between the client and the gateway, and often between the gateway and backend services as well. • Rate limiting caps how many requests a client can make in a given time window, protecting backend services from being overwhelmed or abused. • Input validation and sanitization at the gateway can catch malformed or malicious payloads (like SQL injection or XSS attempts) before they reach internal services.
Example: Spring Cloud Gateway can be configured with a filter that validates a JWT's signature and scope, a RequestRateLimiter filter backed by Redis to cap requests per client, and a filter to strip suspicious characters from query parameters before forwarding the request downstream.
Interview Tip: A concise interview answer is:
"At the gateway I'd enforce authentication and authorization on every request, terminate TLS to encrypt traffic, apply rate limiting to prevent abuse, and validate or sanitize incoming input to catch things like SQL injection or XSS attempts before they ever reach a backend service."