Cache warming strategies in Redis - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

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

Redis

SET "user:1001" "John Doe" [1]

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AXX

BNX

CPX

DEX

Attempts:

3 left

💡 Hint

Common Mistakes

Using EX or PX which set expiration but do not control existence.

Using XX which sets only if key exists, not for warming.

The NX option sets the key only if it does not already exist, which is useful for cache warming to avoid overwriting existing cache.

2fill in blank

medium

Complete the code to preload multiple keys into Redis cache using a pipeline.

Redis

redis.pipeline()[1]

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A.execute()

B.flushall()

C.get('user:1')

D.set('user:1', 'Alice')

Attempts:

3 left

💡 Hint

Common Mistakes

Calling execute immediately without adding commands.

Using flushall which clears the cache.

Using pipeline().set() allows batching multiple set commands to warm the cache efficiently.

3fill in blank

hard

Fix the error in the Lua script that preloads cache keys only if they don't exist.

Redis

if redis.call('EXISTS', [1]) == 0 then redis.call('SET', [1], ARGV[1]) end

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AKEYS[2]

BARGV[1]

CKEYS[1]

DARGV[2]

Attempts:

3 left

💡 Hint

Common Mistakes

Using ARGV for keys causes errors.

Using wrong index in KEYS or ARGV arrays.

In Redis Lua scripts, keys are passed via KEYS array. To check existence of the first key, use KEYS[1].

4fill in blank

hard

Fill both blanks to create a Redis command that preloads keys with expiration only if they don't exist.

Redis

SET [1] [2] NX EX 3600

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Auser:2001

BJohn

Cuser:3001

DAlice

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping key and value positions.

Using keys that do not match the value.

The command sets key user:2001 with value John only if the key does not exist, with expiration of 3600 seconds.

5fill in blank

hard

Fill all three blanks to write a Lua script that warms cache by setting multiple keys with values only if they don't exist.

Redis

for i, key in ipairs([1]) do if redis.call('EXISTS', key) == 0 then redis.call('SET', key, [2][i]) end end return [3]

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

A{'user:1', 'user:2', 'user:3'}

B{'Alice', 'Bob', 'Carol'}

Ctrue

Dfalse

Attempts:

3 left

💡 Hint

Common Mistakes

Using mismatched keys and values.

Returning false instead of true.

Not using tables for keys and values.

The script loops over keys {'user:1', 'user:2', 'user:3'} and sets their values from {'Alice', 'Bob', 'Carol'} only if keys don't exist, then returns true.