HTTP caching headers in Node.js - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the effect of setting Cache-Control: no-store?

In a Node.js HTTP server, if the response header Cache-Control is set to no-store, what will the browser do?

Node.js

res.setHeader('Cache-Control', 'no-store');
res.end('Hello');

A The browser will cache the response only if the user is offline.

B The browser will cache the response but revalidate it with the server before each use.

C The browser will cache the response and use it without checking for updates.

D The browser will not cache the response at all and will fetch it fresh every time.

💡 Hint

Think about what no-store means for caching.

no-store tells the browser not to save any part of the response. It must always get a fresh copy.

📝 Syntax

intermediate

Which code correctly sets a 1-hour cache expiration using Cache-Control?

Choose the Node.js code snippet that correctly sets the Cache-Control header to cache the response for 3600 seconds (1 hour).

A res.setHeader('Cache-Control', 'max-age=3600');

B res.setHeader('Cache-Control', 'maxage=3600');

C res.setHeader('Cache-Control', 'max_age=3600');

D res.setHeader('Cache-Control', 'max age=3600');

💡 Hint

Look for the exact syntax of the max-age directive.

The correct directive is max-age with a hyphen, no spaces.

🔧 Debug

advanced

Why does this Node.js server response never cache despite max-age set?

Consider this Node.js code snippet:

res.setHeader('Cache-Control', 'max-age=3600');
res.setHeader('Pragma', 'no-cache');
res.end('Hello');

Why will the browser not cache this response?

Node.js

res.setHeader('Cache-Control', 'max-age=3600');
res.setHeader('Pragma', 'no-cache');
res.end('Hello');

A Because the response body is too small to cache.

B Because 'max-age' must be set to 0 to enable caching.

C Because the 'Pragma: no-cache' header overrides 'Cache-Control' and disables caching.

D Because 'Cache-Control' and 'Pragma' headers cannot be set together.

💡 Hint

Remember legacy headers can override modern ones.

The 'Pragma: no-cache' header is a legacy HTTP 1.0 header that tells browsers not to cache. It overrides 'Cache-Control' directives.

❓ state_output

advanced

What is the value of the ETag header after this code runs?

Given this Node.js code snippet:

const crypto = require('crypto');
const body = 'Hello World';
const etag = crypto.createHash('md5').update(body).digest('hex');
res.setHeader('ETag', etag);
res.end(body);

What is the value of the ETag header?

Node.js

const crypto = require('crypto');
const body = 'Hello World';
const etag = crypto.createHash('md5').update(body).digest('hex');
res.setHeader('ETag', etag);
res.end(body);

A "etag-123456"

B "b10a8db164e0754105b7a99be72e3fe5"

C "md5:Hello World"

D "Hello World"

💡 Hint

MD5 hash of 'Hello World' is a known fixed value.

The MD5 hash of 'Hello World' is 'b10a8db164e0754105b7a99be72e3fe5'. This is set as the ETag value.

🧠 Conceptual

expert

Which header combination enables client-side caching with validation?

To enable client-side caching where the browser stores the response but checks with the server if it is still valid before using it, which combination of headers should a Node.js server send?

A Cache-Control: max-age=3600, ETag: "abc123"

B Cache-Control: max-age=0, ETag: "abc123"

C Cache-Control: max-age=3600, Pragma: no-cache

D Cache-Control: no-store, Last-Modified: "Wed, 21 Oct 2015 07:28:00 GMT"

💡 Hint

Think about caching duration and validation tokens.

Setting a positive max-age allows caching. Adding an ETag lets the browser validate if the cached copy is still fresh by asking the server.