How to Configure Redis Caching to Speed Up WordPress on Ubuntu 18.04?

Redis is an open-source in-memory data structure store. It can be used as a DB, cache, and DB server that supports various data structures. You can use Redis with a relational database like MYSQL to speed up your website. 

In this article, we will configure Redis as a cache on a WordPress website to load your website faster. In addition, Redis will optimize the time-consuming database queries using its cache. 

A default WordPress website without Redis can load at around 800 ms; with Redis, you can lower it to about 450 ms.

How does caching work?

A database query is performed on your server when the WordPress page loads for the first time; Redis will remember or cache this query. 

Now, when another user tries to load the same WordPress page, the results will be fetched from Redis without querying the database, resulting in faster performance of your website. The object cache of Redis will cache the SQL queries required to load the WordPress pages.

Let us start with installing Redis on Ubuntu 18.04 server. 

1. First, run the update command given below – 

sudo apt update

2. Install Redis with the command as shown below – 

sudo apt install redis-server

3. Once Redis is installed, we will need to configure it as a cache.

4. Add the below line at the end of your redis.conf file. Use the below command to perform this action.

maxmemory 256mb
maxmemory-policy allkeys-lru

5. Save and close the redis.conf file.


Now, we will download the object-cache.php script file, a third-party script. You can read the comments to see how it works.


1. Move this file to the/wp-content folder of the WordPress installation using this command – 

sudo mv object-cache.php /var/www/html/wp-content/

2. We will enable the cache settings in your WordPress config file.
    To do this, edit the wp-config.php  

nano /var/www/html/wp-config.php

3. Add the lines below after the *Authentication Unique Keys and Salts. Section:

define('WP_CACHE_KEY_SALT', '');

 4. To create a persistent cache with the Redis object cache plugin, add this line after the define('WP_CACHE_KEY_SALT,' ''); line – 

define('WP_CACHE', true);

5. Save and close the file.

6. Restart the Redis and Apache files.

Restart Redis:
sudo service redis-server restart

Restart Apache
sudo service apache2 restart

That is it! 

Your WordPress website will now use Redis caching, which will load much faster. 

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