How to Install and Configure Memcached on DirectAdmin for WordPress Performance

Every WordPress page load triggers dozens of MySQL database queries. Without object caching, those queries run every single time — even for identical requests. Memcached solves this by storing the results of expensive database queries in RAM, allowing WordPress to retrieve them in under a millisecond instead of hitting MySQL each time. This guide covers the complete setup of Memcached on DirectAdmin servers: installation, PHP extension configuration, WordPress object cache configuration, and performance verification.

What Memcached Does and When to Use It

Memcached is a distributed in-memory key-value store that acts as a caching layer between WordPress and MySQL. Instead of running a query like "get all posts in category X with their metadata", WordPress stores the result in Memcached RAM and retrieves it from memory on the next request — bypassing MySQL entirely.

Best use cases for Memcached on DirectAdmin:

• WordPress sites with high database query counts (WooCommerce, membership sites, forums)
• Servers where MySQL CPU usage is consistently above 30-40%
• Sites using page caching (Memcached handles object-level caching, page caches handle full-page caching — they complement each other)
• Multi-site WordPress installations

Memcached vs Redis: Both are in-memory caches. Redis supports data persistence (data survives restarts) and more data structures, making it better for session storage and advanced caching. Memcached is simpler, uses less RAM per cached object, and is often faster for pure object caching workloads. Choose Memcached if you already have it on your DirectAdmin server or prefer a lighter footprint; choose Redis if you need persistence or are already using it for sessions.

Step 1: Install Memcached on DirectAdmin

DirectAdmin runs on CentOS, AlmaLinux, CloudLinux, or Debian/Ubuntu. Installation differs slightly by OS.

CentOS / AlmaLinux / CloudLinux

yum install -y memcached libmemcached libmemcached-devel

systemctl start memcached
systemctl enable memcached

systemctl status memcached
# Expected output includes: Active: active (running)

apt-get update
apt-get install -y memcached libmemcached-tools

systemctl start memcached
systemctl enable memcached

PORT="11211"
USER="memcached"
MAXCONN="1024"
CACHESIZE="256"
OPTIONS="-l 127.0.0.1"

-m 256
-l 127.0.0.1
-p 11211

systemctl restart memcached

cd /usr/local/directadmin/custombuild

./build versions | grep php

# Check current options for PHP 8.2 (or your version):
cat options.conf | grep memcache

./build php n
# or for a specific version:
./build php82_memcached

# Install php-memcached via yum (CloudLinux/cPanel-style repos):
yum install -y ea-php82-php-memcached

# Or via PECL:
pecl install memcached

# Enable the extension (add to php.ini or a conf.d file):
echo "extension=memcached.so" > /etc/php.d/memcached.ini

php -m | grep -i memcach

php -r "var_dump(class_exists('Memcached'));"
# Expected: bool(true)

telnet 127.0.0.1 11211
# In the Memcached session:
stats
# You will see output with curr_connections, cmd_get, cmd_set, etc.
quit

<?php
$m = new Memcached();
$m->addServer('127.0.0.1', 11211);
$m->set('test_key', 'memcached_working', 60);
$result = $m->get('test_key');
echo ($result === 'memcached_working') ? 'SUCCESS: Memcached is working' : 'FAILED: Memcached not responding';
?>

memcached-tool 127.0.0.1:11211 stats

memcached-tool 127.0.0.1:11211 stats | grep -E "cmd_get|get_hits|get_misses"

Hit Rate = get_hits / (get_hits + get_misses) * 100

memcached-tool 127.0.0.1:11211 stats | grep bytes
# curr_bytes: current memory in use
# limit_maxbytes: your configured limit

Step 7: DirectAdmin Multi-PHP Version Considerations

If you run multiple PHP versions on your DirectAdmin server (e.g., PHP 7.4 and PHP 8.2 for different domains), the Memcached extension must be installed for each PHP version your WordPress sites use.

# Check which PHP version each domain uses:
cat /usr/local/directadmin/data/users/username/domains/yourdomain.com.conf | grep php

# Build Memcached extension for additional PHP versions:
cd /usr/local/directadmin/custombuild
./build php74_memcached
./build php82_memcached

After building, restart PHP-FPM for each version:

systemctl restart php74-fpm
systemctl restart php82-fpm

Troubleshooting Common Memcached Issues on DirectAdmin

PHP extension not loading: Run php -m | grep memcach — if empty, the extension is not installed for the active PHP CLI version. Check /etc/php.d/ or /usr/local/lib/php.ini for the extension directive.

WordPress not using Memcached after plugin setup: Check that a object-cache.php drop-in file is NOT already in wp-content/ — a conflicting drop-in from another plugin overrides your setup.

Memcached evicting too aggressively: Increase CACHESIZE in the Memcached config. You can also reduce cache lifetime (TTL) values in W3 Total Cache to keep only fresh, frequently-used objects.

Port 11211 not responding: Confirm Memcached is bound to 127.0.0.1 and running: ss -tlnp | grep 11211

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