REST Lens

Category: HTTP Headers

Description

GET operations should include caching headers (Cache-Control, Expires, or Pragma) in their responses to support proper HTTP caching behavior.

What It Checks

This rule examines GET operations and their 2XX responses for caching header definitions:

Cache-Control - Primary caching directive
Expires - Legacy expiration header
Pragma - HTTP/1.0 compatibility

Why It Matters

Proper caching headers enable:

Performance: Reduced server load and faster responses
Bandwidth Savings: Clients can use cached responses
Scalability: Better resource utilization
User Experience: Faster page loads for cached resources

Examples

Good

paths:
  /users:
    get:
      operationId: getUsers
      responses:
        '200':
          description: List of users
          headers:
            Cache-Control:
              schema:
                type: string
              description: Caching directive
          content:
            application/json:
              schema:
                type: array

Bad

paths:
  /users:
    get:
      operationId: getUsers
      responses:
        '200':
          description: List of users
          # No caching headers defined
          content:
            application/json:
              schema:
                type: array

Exceptions

Non-GET operations (POST, PUT, etc.)
Operations returning sensitive data that shouldn't be cached
Real-time data endpoints

Configuration

This rule has no configuration options. It is either enabled or disabled.

Related Rules

Rule 58: Last-Modified - Last modification timestamp
Rule 59: ETag Headers - Entity tag for caching
Rule 60: Conditional PUT - Conditional request support

Caching Headers