Authentication

The process of verifying the identity of a user or system.

Authentication is the process of verifying the identity of a user, device, or system attempting to access a resource. It answers the question "who are you?" and typically involves presenting credentials such as a username and password, an API key, a token, or a certificate.

Common authentication methods in API contexts include API keys, OAuth 2.0 tokens, JSON Web Tokens (JWT), and mutual TLS. Each method has different security characteristics and is suited to different use cases. API keys are simple but offer limited security, while OAuth 2.0 provides delegated authorization flows suitable for third-party access.

API gateways commonly handle authentication as a centralized concern, validating credentials before requests reach backend services. This offloads authentication logic from individual services, ensures consistent enforcement, and simplifies the security architecture. In serverless deployments, gateway-level authentication is particularly important since there is no persistent server to maintain session state.