Cache invalidation strategies in Django - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set a cache key with a timeout in Django.

Django

cache.set('user_123', user_data, timeout=[1])

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

A300

B'300'

CNone

D'None'

Attempts:

3 left

💡 Hint

Common Mistakes

Using quotes around numbers for timeout

Setting timeout to None as a string

The timeout value should be an integer representing seconds. Here, 300 means the cache expires after 5 minutes.

2fill in blank

medium

Complete the code to delete a cache key in Django.

Django

cache.[1]('user_123')

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

Adelete

Bclear

Cremove

Dpop

Attempts:

3 left

💡 Hint

Common Mistakes

Using clear deletes all cache, not a single key

Using pop is not a cache method

The delete method removes a specific key from the cache.

3fill in blank

hard

Fix the error in the code to invalidate cache after updating a model instance.

Django

def save(self, *args, **kwargs):
    super().save(*args, **kwargs)
    cache.[1](f'user_{self.id}')

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

Aclear

Bdelete

Cset

Dget

Attempts:

3 left

💡 Hint

Common Mistakes

Using clear removes all cache

Using set overwrites cache instead of invalidating

After saving the model, we delete the cache key to invalidate stale data.

4fill in blank

hard

Fill both blanks to create a cache key and set it with a timeout.

Django

cache_key = f'user_[1]'
cache.[2](cache_key, user_data, timeout=600)

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

Aid

Bset

Cdelete

Dpk

Attempts:

3 left

💡 Hint

Common Mistakes

Using delete instead of set

Using pk when id is expected

The cache key uses the user's id. The set method stores data with a timeout.

5fill in blank

hard

Fill all three blanks to check cache, set if missing, and return data.

Django

cache_key = f'user_[1]'
data = cache.[2](cache_key)
if data is None:
    data = get_user_data([3])
    cache.set(cache_key, data, timeout=300)
return data

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

Aid

Bget

Cuser_id

Dpk

Attempts:

3 left

💡 Hint

Common Mistakes

Using set instead of get to retrieve data

Using pk instead of user_id in function call

The cache key uses id. We try to get cached data. If missing, we fetch data using user_id and cache it.