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Challenge - 5 Problems
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Test your skills under time pressure!
🧠 Conceptual
intermediate2:00remaining
Why use statelessness in REST APIs?
In REST, statelessness means each request from client to server must contain all the information needed to understand and process the request. Why is this important?
Attempts:
2 left
💡 Hint
Think about how servers handle many users at once without mixing their data.
✗ Incorrect
Statelessness means the server does not keep client context between requests. This makes scaling easier because any server can handle any request without needing previous information.
❓ component_behavior
intermediate2:00remaining
What happens if REST APIs don't use proper HTTP methods?
Consider a REST API built with Express that uses POST for all actions, including data retrieval. What is a likely consequence?
Attempts:
2 left
💡 Hint
Think about how browsers and proxies handle GET vs POST requests.
✗ Incorrect
Using POST for all actions prevents caching because POST requests are not cached by default. This can slow down the API and increase server load.
❓ state_output
advanced2:00remaining
What is the output of this Express route following REST principles?
Given this Express route, what JSON response will the client receive when requesting GET /users/42?
```js
const express = require('express');
const app = express();
const users = { 42: { id: 42, name: 'Alice' } };
app.get('/users/:id', (req, res) => {
const user = users[req.params.id];
if (!user) {
return res.status(404).json({ error: 'User not found' });
}
res.json(user);
});
// Assume server is running and client requests GET /users/42
```
Express
const express = require('express'); const app = express(); const users = { 42: { id: 42, name: 'Alice' } }; app.get('/users/:id', (req, res) => { const user = users[req.params.id]; if (!user) { return res.status(404).json({ error: 'User not found' }); } res.json(user); });
Attempts:
2 left
💡 Hint
Look at how the user object is retrieved and returned as JSON.
✗ Incorrect
The route finds the user with id 42 and returns it as JSON with status 200. The id is a number, so the JSON reflects that.
📝 Syntax
advanced2:00remaining
Which Express route correctly implements RESTful DELETE for a resource?
Choose the correct Express route syntax to delete a user by id following REST principles.
Attempts:
2 left
💡 Hint
REST uses HTTP DELETE method to remove resources.
✗ Incorrect
RESTful APIs use the DELETE method on the resource URL to delete it. Using POST, GET, or PUT for delete actions breaks REST conventions.
🔧 Debug
expert3:00remaining
Why does this Express REST API fail to scale properly?
Consider this Express server code snippet:
```js
const express = require('express');
const app = express();
let sessionData = {};
app.post('/login', (req, res) => {
const userId = req.body.userId;
sessionData[userId] = { loggedIn: true };
res.json({ message: 'Logged in' });
});
app.get('/profile', (req, res) => {
const userId = req.query.userId;
if (sessionData[userId]?.loggedIn) {
res.json({ profile: 'User profile data' });
} else {
res.status(401).json({ error: 'Not logged in' });
}
});
app.listen(3000);
```
What is the main reason this design violates REST principles and causes scaling problems?
Express
const express = require('express'); const app = express(); let sessionData = {}; app.post('/login', (req, res) => { const userId = req.body.userId; sessionData[userId] = { loggedIn: true }; res.json({ message: 'Logged in' }); }); app.get('/profile', (req, res) => { const userId = req.query.userId; if (sessionData[userId]?.loggedIn) { res.json({ profile: 'User profile data' }); } else { res.status(401).json({ error: 'Not logged in' }); } }); app.listen(3000);
Attempts:
2 left
💡 Hint
Think about what statelessness means for REST and how storing data in memory affects multiple servers.
✗ Incorrect
REST requires stateless servers. Storing session data in memory means requests depend on server memory, so scaling with multiple servers fails because session data is not shared.