Validation-based caching in Rest API - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is validation-based caching in REST APIs?

Validation-based caching is a technique where the server tells the client if the cached data is still valid using validators like ETag or Last-Modified headers, avoiding sending the full data again.

beginner

What does the ETag header do in validation-based caching?

ETag is a unique identifier for a specific version of a resource. The client sends it back in If-None-Match header to ask if the resource changed. If not, the server replies with 304 Not Modified.

beginner

How does the Last-Modified header help with validation-based caching?

Last-Modified tells when the resource was last changed. The client sends this date in If-Modified-Since header. If the resource is unchanged, the server responds with 304 Not Modified.

beginner

What HTTP status code indicates that cached data is still valid?

The HTTP status code 304 Not Modified means the cached data is still valid and the server does not resend the resource body.

beginner

Why is validation-based caching better than no caching?

It saves bandwidth and speeds up responses by letting clients reuse cached data when it hasn't changed, while still ensuring data freshness by validating with the server.

Which HTTP header is used by the client to ask if the cached resource has changed using ETag?

A If-None-Match

B If-Modified-Since

C Cache-Control

D ETag

The client sends the ETag value in the If-None-Match header to check if the resource has changed.

What response status code does the server send if the cached resource is still valid?

A 500 Internal Server Error

B 404 Not Found

C 200 OK

D 304 Not Modified

304 Not Modified tells the client the cached resource is still valid and no new data is sent.

Which header tells the client when the resource was last changed?

A Last-Modified

B Content-Type

C ETag

D Expires

Last-Modified header contains the date/time when the resource was last updated.

What does the client send in the If-Modified-Since header?

A The ETag value

B The last modified date it has cached

C The full resource data

D The cache expiration time

The client sends the date of the cached resource in If-Modified-Since to check if it is still fresh.

Why use validation-based caching instead of no caching?

A To disable caching completely

B To always get fresh data without delay

C To reduce bandwidth and improve speed by reusing unchanged data

D To force the server to send full data every time

Validation-based caching saves bandwidth and speeds up responses by reusing cached data when valid.

Explain how validation-based caching works in REST APIs using ETag and Last-Modified headers.

Think about how the client asks the server if cached data is still fresh.

Why is the 304 Not Modified status code important in validation-based caching?

Consider what happens when the server confirms data hasn't changed.