Write-behind pattern in Redis - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add a key-value pair to Redis cache.

Redis

redis_client.[1]('user:1', 'John Doe')

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

Aexpire

Bset

Cget

Ddelete

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'get' instead of 'set' to store data.

Using 'expire' which sets a timeout, not stores data.

The set command stores a key-value pair in Redis.

2fill in blank

medium

Complete the code to retrieve the value of a key from Redis cache.

Redis

value = redis_client.[1]('user:1')

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

Aget

Bset

Cdelete

Dexists

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'set' instead of 'get' to retrieve data.

Using 'exists' which only checks if a key exists.

The get command retrieves the value of a key from Redis.

3fill in blank

hard

Fix the error in the code to schedule a write-behind update after caching.

Redis

def update_cache_and_db(key, value):
    redis_client.set(key, value)
    schedule_write_[1](key, value)

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

Aahead

Bnow

Cbehind

Ddelete

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'schedule_write_ahead' which is the opposite pattern.

Using 'schedule_write_now' which is immediate writing, not delayed.

The write-behind pattern schedules updates to the database after caching, so schedule_write_behind is the correct function name.

4fill in blank

hard

Fill both blanks to create a dictionary for pending writes with keys and values.

Redis

pending_writes = { [1]: [2] for [1] in cache_keys }

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Akey

Bcache[key]

Cvalue

Dcache[value]

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'value' as the loop variable which is undefined.

Using 'cache[value]' which is incorrect indexing.

We use key as the dictionary key and cache[key] as the value to map keys to their cached values.

5fill in blank

hard

Fill all three blanks to filter keys with pending writes and update the database.

Redis

for [1] in pending_writes:
    if pending_writes[[2]] [3] None:
        update_database([1], pending_writes[[2]])

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

Akey

C!=

D==

Attempts:

3 left

💡 Hint

Common Mistakes

Using '==' instead of '!=' which would skip updates.

Using different variable names for loop and dictionary access.

We loop over key, check if the value is not None using !=, then update the database.