An authorizer is a specialized piece of middleware or code that intercepts incoming API requests to validate the requester’s identity and determine their access permissions before they reach backend services. While open-source solutions like the Authorizer.dev Platform exist for self-hosted OAuth2 environments, the term most commonly refers to AWS API Gateway Lambda Authorizers used to secure serverless applications. Core Types of Authorizers
When implementing a custom authorizer, you must choose how your system evaluates incoming data:
Token-Based (TOKEN): Evaluates a single identity string, typically a JSON Web Token (JWT) or an OAuth bearer token passed via the Authorization header.
Request-Based (REQUEST): Evaluates a broader set of parameters, including headers, query string parameters, stage variables, and path context. Step-by-Step Implementation Workflow
Securing your endpoints follows a sequential pattern from code deployment to endpoint execution:
Extract the Token: Read incoming client metadata from the request header.
Validate Identity: Verify the token’s cryptographic signature against an Identity Provider (IdP).
Generate Permissions: Build an Identity and Access Management (IAM) policy file specifying allowed or denied methods.
Evaluate Routing: API Gateway evaluates the policy to either trigger backend processing or return a 403 Forbidden error.
Client Request ──> API Gateway ──> Lambda Authorizer ──> IdP Validation │ Backend Lambda <── [Allow Policy] <──────┴──────> [Deny Policy] ──> 403 Forbidden Essential Performance Optimization Strategies
Building an efficient authorization layer requires balancing deep security check constraints with minimal latency: Enable Token Caching
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