Cache invalidation strategies in Express - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set a cache expiration time in Express middleware.

Express

app.use((req, res, next) => {
  res.set('Cache-Control', 'public, max-age=[1]');
  next();
});

Drag options to blanks, or click blank then click option'

Aexpires

Bcache

C3600

Dno-cache

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'cache' or 'expires' instead of a numeric value.

Setting 'no-cache' which disables caching instead of setting expiration.

The max-age directive sets the cache expiration time in seconds. Here, 3600 means the cache expires after one hour.

2fill in blank

medium

Complete the code to clear a specific cache key in an Express route.

Express

app.get('/clear-cache', (req, res) => {
  cache.[1]('user-data');
  res.send('Cache cleared');
});

Drag options to blanks, or click blank then click option'

Adelete

Bget

Cset

Dclear

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'get' which only retrieves data.

Using 'clear' which removes all cache entries.

The delete method removes a specific key from the cache.

3fill in blank

hard

Fix the error in the cache middleware to properly invalidate cache after response.

Express

app.use((req, res, next) => {
  res.on('finish', () => {
    cache.[1](req.originalUrl);
  });
  next();
});

Drag options to blanks, or click blank then click option'

Adelete

Binvalidate

Cset

Dclear

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'set' which adds or updates cache instead of removing.

Using 'invalidate' which is not a standard method.

The delete method is used to remove the cache entry for the requested URL after the response finishes.

4fill in blank

hard

Fill both blanks to create a cache middleware that skips caching for authenticated users.

Express

app.use((req, res, next) => {
  if (req.user && req.user.[1]) {
    res.set('Cache-Control', '[2]');
  }
  next();
});

Drag options to blanks, or click blank then click option'

AisAuthenticated

Bno-store

Cpublic

DisAdmin

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'isAdmin' instead of 'isAuthenticated'.

Setting 'public' which allows caching instead of disabling it.

The middleware checks if the user is authenticated using isAuthenticated. If true, it sets Cache-Control to no-store to prevent caching sensitive data.

5fill in blank

hard

Fill all three blanks to implement a cache invalidation strategy that clears cache on data update.

Express

app.post('/update-data', (req, res) => {
  updateDatabase(req.body);
  cache.[1](req.body.[2]);
  res.status(200).send({ message: '[3]' });
});

Drag options to blanks, or click blank then click option'

Adelete

Bid

CData updated and cache cleared

Dset

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'set' instead of 'delete' to remove cache.

Using wrong key like 'key' instead of 'id'.

Sending a generic message instead of a clear confirmation.

After updating the database, the cache entry identified by id is deleted using delete. Then a success message is sent.