Cache drivers (file, Redis, Memcached) in Laravel - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What happens when you cache data using the file driver in Laravel?

Consider this Laravel code snippet that caches a value using the file cache driver:

Cache::store('file')->put('key', 'value', 600);

What is the behavior of this code?

Laravel

Cache::store('file')->put('key', 'value', 600);

A It stores the value in Memcached for 600 seconds.

B It stores the value in Redis for 600 seconds.

C It stores the value in a file inside the storage/framework/cache/data directory for 600 seconds.

D It stores the value in the database cache table for 600 seconds.

💡 Hint

Think about where the file cache driver saves data by default in Laravel.

The file cache driver stores cached data as files inside the storage/framework/cache/data directory. The number 600 means the cache expires after 600 seconds (10 minutes).

📝 Syntax

intermediate

Which code correctly retrieves a cached value from Redis in Laravel?

You want to get the cached value stored under 'user_1' using the Redis cache driver. Which code snippet is correct?

A Cache::redis()->get('user_1');

B Cache::store('redis')->get('user_1');

C Cache::get('redis', 'user_1');

D Cache::store('memcached')->get('user_1');

💡 Hint

Use the store method with the driver name to specify Redis.

The correct way to use a specific cache driver is Cache::store('driver')->get('key'). Option B uses 'redis' as the driver and gets the key correctly.

🔧 Debug

advanced

Why does caching with Memcached fail in this Laravel code?

Given this code:

Cache::store('memcached')->put('session', 'data', 300);

The cache is not storing the value as expected. What is the most likely cause?

Laravel

Cache::store('memcached')->put('session', 'data', 300);

A Memcached extension is not installed or enabled on the server.

B The cache key 'session' is reserved and cannot be used.

C The expiration time 300 is too short and ignored by Memcached.

D Laravel does not support Memcached as a cache driver.

💡 Hint

Check if the server has the required PHP extension for Memcached.

Memcached requires the PHP Memcached extension installed and enabled. Without it, Laravel cannot use Memcached and caching fails silently or throws errors.

❓ state_output

advanced

What is the output of this Laravel cache code using Redis?

Assume Redis cache is working. What does this code output?

Cache::store('redis')->put('count', 5, 60);
Cache::store('redis')->increment('count');
echo Cache::store('redis')->get('count');

Laravel

Cache::store('redis')->put('count', 5, 60);
Cache::store('redis')->increment('count');
echo Cache::store('redis')->get('count');

A 6

B 5

C null

D Error: increment method not found

💡 Hint

Increment increases the stored number by one.

The code stores 5 under 'count', then increments it by 1, so the final value is 6.

🧠 Conceptual

expert

Which cache driver is best suited for storing session data in a distributed Laravel app and why?

You have a Laravel app running on multiple servers behind a load balancer. You want to store session data in cache for fast access and sharing between servers. Which cache driver should you choose and why?

A Database, because it is the fastest cache driver for session data.

B File, because it stores data locally and is fastest for distributed apps.

C Memcached, because it stores data on disk and is persistent across server restarts.

D Redis, because it supports fast in-memory storage and shared access across servers.

💡 Hint

Think about shared access and speed for multiple servers.

Redis is an in-memory data store that supports fast access and sharing data across multiple servers, making it ideal for distributed session storage.

Practice

1. Which Laravel cache driver stores cached data as files on the local server?

easy

A. memcached

B. file

C. redis

D. database

Solution

1. Step 1: Understand cache driver types in Laravel

   Laravel supports multiple cache drivers like file, redis, memcached, and database.

2. Step 2: Identify the driver that uses local files

   The 'file' driver stores cache data as files on the local server's disk.

3. Final Answer:

   file -> Option B

4. Quick Check:

   Local file storage = file [OK]

Hint: File driver means cache saved as local files [OK]

Common Mistakes:

• Confusing Redis or Memcached as file storage
• Thinking database driver stores files
• Assuming 'file' driver is remote cache

2. Which is the correct way to set Redis as the cache driver in Laravel's config/cache.php file?

easy

A. 'default' => 'redis',

B. 'driver' => 'redis',

C. 'cache_driver' => 'redis',

D. 'cache' => 'redis',

Solution

1. Step 1: Locate the cache driver setting in config/cache.php

   The main cache driver is set by the 'default' key in the config array.

2. Step 2: Confirm correct syntax for Redis driver

   Setting 'default' => 'redis' tells Laravel to use Redis as the cache driver.

3. Final Answer:

   'default' => 'redis' -> Option A

4. Quick Check:

   Default key sets cache driver = 'default' [OK]

Hint: Set 'default' key to driver name in config/cache.php [OK]

Common Mistakes:

• Using 'driver' instead of 'default' key
• Writing 'cache_driver' which is invalid
• Confusing config keys with environment variables

3. Given this Laravel code snippet using Redis cache driver:

Cache::put('user_1', 'Alice', 3600);
$name = Cache::get('user_1');

What will be the value of $name immediately after this code runs?

medium

A. "Alice"

B. null

C. "user_1"

D. 3600

Solution

1. Step 1: Understand Cache::put usage

   Cache::put stores the value 'Alice' with key 'user_1' for 3600 seconds (1 hour).

2. Step 2: Retrieve cached value with Cache::get

   Cache::get('user_1') returns the stored value 'Alice' if it exists and is not expired.

3. Final Answer:

   "Alice" -> Option A

4. Quick Check:

   Cache get returns stored value = "Alice" [OK]

Hint: Cache::get returns stored value if not expired [OK]

Common Mistakes:

• Expecting key name instead of value
• Confusing expiration time as returned value
• Assuming null because of Redis driver

4. What is wrong with this Laravel cache configuration snippet for Memcached in config/cache.php?

'memcached' => [
    'driver' => 'memcached',
    'servers' => [
        ['host' => '127.0.0.1', 'port' => 11211],
    ],
],

Why might this cause an error?

medium

A. Driver name should be 'memcache' not 'memcached'

B. Port number 11211 is incorrect for Memcached

C. Missing 'weight' key in the server array

D. Host IP must be 'localhost' not '127.0.0.1'

Solution

1. Step 1: Check Memcached server config requirements

   Laravel expects each Memcached server array to include 'host', 'port', and 'weight' keys.

2. Step 2: Identify missing 'weight' key

   The given config lacks the 'weight' key, which can cause errors when connecting to Memcached.

3. Final Answer:

   Missing 'weight' key in the server array -> Option C

4. Quick Check:

   Memcached servers need 'weight' key [OK]

Hint: Memcached server config must include 'weight' [OK]

Common Mistakes:

• Assuming port 11211 is wrong (it's default)
• Confusing driver name with 'memcache'
• Thinking host IP must be 'localhost'

5. You want to cache user profile data using Redis in Laravel, but only for 10 minutes. Which code snippet correctly sets this with expiration?

hard

A. Cache::put('profile_123', $profileData, 600);

B. Cache::put('profile_123', $profileData, now()->addSeconds(300));

C. Cache::put('profile_123', $profileData, 5);

D. Cache::put('profile_123', $profileData, now()->addMinutes(10));

Solution

1. Step 1: Understand Cache::put expiration parameter

   Laravel's Cache::put accepts expiration as an integer number of minutes, or a Carbon/DateTime instance.

2. Step 2: Use now()->addMinutes(10) for 10 minutes expiration

   Passing now()->addMinutes(10) sets expiration 10 minutes from current time correctly.

3. Step 3: Analyze other options

   A uses 600 (600 minutes = 10 hours), too long; C uses 5 minutes, too short; D uses now()->addSeconds(300) (5 minutes), too short.

4. Final Answer:

   Cache::put('profile_123', $profileData, now()->addMinutes(10)); -> Option D

5. Quick Check:

   Use now()->addMinutes(10) for 10 min cache [OK]

Hint: Use now()->addMinutes(10) for 10-minute cache expiration [OK]

Common Mistakes:

• Using 600 which is 600 minutes (10 hours)
• Using small integer 5 (5 minutes)
• Using addSeconds(300) which is 5 minutes