REST API Caching with HTTP Headers Quiz Quiz

Assess your skills in managing REST API caching strategies using essential HTTP headers. Enhance your understanding of cache control principles, header functions, and response optimization for effective web API performance.

1. Understanding the Purpose of Cache-Control

   Which HTTP header allows the server to specify caching policies, such as 'no-cache' or 'max-age=3600', in REST API responses?

   1. Cache-Control
   2. Control-Cache
   3. Expires
   4. Cache-Directive

   Explanation: Cache-Control is the standard HTTP header that enables servers to indicate caching policies, such as 'no-cache' to prevent storage or 'max-age' for expiry time. 'Cache-Directive' and 'Control-Cache' are not valid HTTP header names and are sometimes mistakenly referenced. The 'Expires' header can set an expiration date but does not support as granular or dynamic control as 'Cache-Control'. Therefore, Cache-Control is the correct choice for modern caching strategies.

2. Role of the ETag Header

   In a REST API, what is the primary purpose of the ETag HTTP header included in a server response?

   1. To indicate the language of the content
   2. To identify the version of a resource for cache validation
   3. To specify the maximum cache time
   4. To encrypt the payload

   Explanation: The ETag header sends a unique value representing the specific version of a resource, helping with cache validation and conditional requests. It is not involved in specifying language (which is done by Content-Language), defining cache time (handled by Cache-Control or Expires), or encrypting data. Therefore, using ETag helps clients know when a resource has changed and should be refetched.

3. Choosing the Best Header for Expiry Date

   If you want to specify an exact expiration date and time for a cached REST API response, which HTTP header should you use?

   1. Age
   2. Expires
   3. If-None-Match
   4. Last-Modified

   Explanation: The Expires header assigns a specific date and time after which the response is considered stale. Last-Modified indicates the last update time of the resource but does not directly control expiry. If-None-Match is used with ETag for conditional requests, and Age represents the time since the resource was fetched from the server. Only Expires lets you define an explicit expiry moment.

4. Cache Validation Using Conditional Requests

   When a REST API client sends a request with the 'If-Modified-Since' header, which HTTP status code is most appropriate if the resource hasn't changed?

   1. 200 OK
   2. 404 Not Found
   3. 304 Not Modified
   4. 201 Created

   Explanation: The 304 Not Modified status code signals that the resource has not changed and the client's cached version is still valid. Returning 200 OK would unnecessarily resend the resource, 404 Not Found means the resource doesn't exist, and 201 Created is used for new resources. Using 304 saves bandwidth and is ideal for conditional GET requests with 'If-Modified-Since'.

5. Effect of 'no-store' Directive in REST API Caching

   What is the effect of including 'Cache-Control: no-store' in the header of a REST API response?

   1. The response may be cached by proxies but not by browsers
   2. The response must not be stored in any cache at all
   3. The response is encrypted before delivery
   4. The response can be cached only for one minute

   Explanation: 'Cache-Control: no-store' directs both browsers and proxies not to cache or store the response under any circumstance. It does not allow even short-term caching. The directive is not about encryption or limiting caching to proxies. Therefore, its primary use is to ensure that sensitive or dynamic data is never cached anywhere.