Cache drivers (file, Redis, Memcached) in Laravel - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of cache drivers in Laravel?

Cache drivers in Laravel store data temporarily to speed up application performance by reducing repeated database or API calls.

beginner

How does the file cache driver work in Laravel?

The file cache driver stores cached data as files on the server's disk, making it simple but slower compared to memory-based caches.

intermediate

What are the advantages of using Redis as a cache driver?

Redis stores cache data in memory, offering very fast read/write speeds and supports advanced data structures like lists and sets.

intermediate

What is Memcached and how is it used in Laravel caching?

Memcached is a high-performance, distributed memory caching system used in Laravel to store data in RAM for quick access and reduce database load.

beginner

When should you choose file cache over Redis or Memcached in Laravel?

Choose file cache for simple or small projects without complex caching needs or when you don't have Redis or Memcached installed.

Which Laravel cache driver stores data as files on the server?

A Memcached

B Redis

C File

D Database

The file cache driver saves cached data as files on the server's disk.

What is a key benefit of using Redis as a cache driver?

A Stores data on disk for persistence

B Supports advanced data structures and fast memory access

C Uses SQL queries for caching

D Caches data only for one second

Redis stores data in memory and supports advanced data types, making it very fast.

Memcached is best described as:

A A distributed memory caching system

B A file-based cache system

C A database caching driver

D A PHP extension for caching

Memcached is a distributed memory caching system used to speed up applications.

Which cache driver would be simplest to set up without extra services?

A Redis

B Memcached

C Database

D File

File cache requires no additional services and stores cache as files.

Why might you avoid using file cache for high-traffic Laravel apps?

A It is slower than memory-based caches like Redis or Memcached

B It stores data in memory only

C It is too fast and causes errors

D It requires complex setup

File cache is slower because it reads/writes to disk, unlike Redis or Memcached which use memory.

Explain the differences between file, Redis, and Memcached cache drivers in Laravel.

Think about storage location and speed.

Describe when and why you would choose Redis or Memcached over file cache in a Laravel project.

Consider project size and speed requirements.

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