An object cache keeps the results of repeated database queries in memory so WordPress does less work per page. Redis is a fast, widely used backend for it. This guide sets Redis up safely on a single server.

What does a Redis object cache do for WordPress? #

It stores query results and computed values in RAM, so repeat requests skip the database. Logged-in pages, admin screens, and dynamic content benefit most because full-page caches cannot serve them. Expect fewer database queries and lower response times on busy sites.

Step 1: Install and secure Redis #

sudo apt install -y redis-server
sudo nano /etc/redis/redis.conf

# /etc/redis/redis.conf
bind 127.0.0.1 -::1
protected-mode yes
maxmemory 256mb
maxmemory-policy allkeys-lru
supervised systemd

Step 2: Restart and test #

sudo systemctl restart redis-server
redis-cli ping   # expect: PONG

Step 3: Connect WordPress #

Add the connection constants to wp-config.php above the line that says to stop editing, then enable your object-cache plugin.

define( 'WP_REDIS_HOST', '127.0.0.1' );
define( 'WP_REDIS_PORT', 6379 );
define( 'WP_CACHE_KEY_SALT', 'example.com:' );

Check that it is working #

1. Load a few pages while logged out and logged in.
2. Run redis-cli info stats and compare keyspace_hits with keyspace_misses.
3. A healthy site shows hits far above misses after the cache warms up.