Apex Cache Pro Documentation

Apex Cache Pro replaces the default WordPress object cache with a hardened, Redis-backed persistent cache engine. It dramatically reduces database load by storing computed results in Redis — an in-memory data store that responds in sub-millisecond time.

Unlike the built-in WordPress transient and object cache (which is non-persistent by default), Apex Cache Pro persists cached objects across requests, meaning the database is only hit when the cache is cold or explicitly invalidated.

The plugin supports single Redis instances, Redis Cluster, and Redis Sentinel topologies. It works with phpredis, Predis, and Relay clients, and includes full multisite support with per-site cache isolation.

Component	Minimum	Recommended
WordPress	5.6+	6.4+
PHP	7.4+	8.2+
Redis Server	6.0+	7.2+
PHP Extension	phpredis 5.0+ or Predis 2.0+	phpredis 6.0+ or Relay

Via WordPress Admin

1. Purchase a license at apexstack.cloud/pricing
2. Download the plugin ZIP from your account dashboard
3. In WordPress, go to Plugins → Add New → Upload Plugin
4. Upload the ZIP file and click Install Now
5. Click Activate Plugin

Via WP-CLI

# Upload and activate
wp plugin install /path/to/apex-cache-pro.zip --activate

# Verify installation
wp plugin list --name=apex-cache-pro --format=table

Via Dashboard

Navigate to Settings → Apex Cache Pro → License and enter your license key. Click Activate. The plugin will verify your key against the Apex Stack license server and enable all features.

Via WP-CLI

# Activate license
wp apex-cache license activate YOUR-LICENSE-KEY

# Check license status
wp apex-cache license status

# Deactivate (e.g., before migrating to a new server)
wp apex-cache license deactivate

Configure the Redis connection by adding constants to your wp-config.php file, before the line that says /* That's all, stop editing! */.

/* Redis connection */
define('APEX_REDIS_HOST', '127.0.0.1');
define('APEX_REDIS_PORT', 6379);
define('APEX_REDIS_PASSWORD', 'your-redis-password');
define('APEX_REDIS_DATABASE', 0);
define('APEX_REDIS_PREFIX', 'wp_');

Constant	Default	Description
APEX_REDIS_HOST	127.0.0.1	Redis server hostname or IP address
APEX_REDIS_PORT	6379	Redis server port
APEX_REDIS_PASSWORD	null	Redis AUTH password (or ACL user:pass)
APEX_REDIS_DATABASE	0	Redis database index (0-15)
APEX_REDIS_PREFIX	wp_	Key prefix to namespace this site's cache

TLS / SSL Connections

For encrypted connections (e.g., AWS ElastiCache with in-transit encryption):

define('APEX_REDIS_SCHEME', 'tls');
define('APEX_REDIS_SSL_VERIFY', true);    // Verify server certificate
define('APEX_REDIS_SSL_CA', '/path/to/ca.pem'); // Optional CA bundle

Apex Cache Pro supports three Redis client libraries. Set the client in wp-config.php:

define('APEX_REDIS_CLIENT', 'phpredis'); // 'phpredis', 'predis', or 'relay'

Client	Type	Performance	Requirements
phpredis	C extension	Fast	pecl install redis
Predis	PHP library	Good	Bundled with plugin
Relay	C extension + shared memory	Fastest	Separate license

Redis Cluster

For Redis Cluster deployments, define an array of cluster nodes:

define('APEX_REDIS_CLUSTER', [
    'tcp://redis-node-1:6379',
    'tcp://redis-node-2:6379',
    'tcp://redis-node-3:6379',
]);

// Optional: cluster-specific settings
define('APEX_REDIS_CLUSTER_FAILOVER', 'error'); // 'none', 'error', 'distribute'

Redis Sentinel

For Redis Sentinel (high-availability) deployments:

define('APEX_REDIS_SENTINELS', [
    'tcp://sentinel-1:26379',
    'tcp://sentinel-2:26379',
    'tcp://sentinel-3:26379',
]);
define('APEX_REDIS_SENTINEL_SERVICE', 'mymaster');

Apex Cache Pro fully supports WordPress Multisite. By default, each sub-site gets its own cache prefix based on the blog ID.

// Share cache across all sites (use with caution)
define('APEX_REDIS_MULTISITE_GLOBAL', true);

// Control network-wide flush behavior
define('APEX_REDIS_MULTISITE_FLUSH', 'site'); // 'site' or 'network'

Constant	Default	Description
APEX_REDIS_MULTISITE_GLOBAL	false	If true, all sites share the same cache namespace
APEX_REDIS_MULTISITE_FLUSH	site	Whether flushing affects just the current site or the entire network

// Maximum TTL for cached objects (seconds, 0 = no limit)
define('APEX_REDIS_MAXTTL', 0);

// Connection timeout (seconds)
define('APEX_REDIS_TIMEOUT', 1);

// Read timeout (seconds)
define('APEX_REDIS_READ_TIMEOUT', 1);

// Retry interval on connection failure (milliseconds)
define('APEX_REDIS_RETRY_INTERVAL', 100);

// Cache groups that should NOT be persisted in Redis
define('APEX_REDIS_IGNORED_GROUPS', [
    'counts', 'plugins', 'themes',
]);

// Cache groups that should NOT be flushed
define('APEX_REDIS_UNFLUSHABLE_GROUPS', [
    'user_meta', 'userslugs',
]);

Apex Cache Pro provides a full set of WP-CLI commands under the wp apex-cache namespace.

Command	Description
wp apex-cache status	Display cache connection status and statistics
wp apex-cache enable	Install the object cache drop-in
wp apex-cache disable	Remove the object cache drop-in
wp apex-cache flush	Flush the entire object cache
wp apex-cache diagnostics	Run connection and performance diagnostics
wp apex-cache license	Manage license activation

wp apex-cache status

Displays current cache connection info, hit/miss ratio, memory usage, and key count.

$ wp apex-cache status

+-----------------+---------------------+
| Property        | Value               |
+-----------------+---------------------+
| Status          | Connected           |
| Client          | phpredis 6.0.2      |
| Host            | 127.0.0.1:6379      |
| Database        | 0                   |
| Key Prefix      | wp_                 |
| Keys            | 4,281               |
| Memory Used     | 12.4 MB             |
| Hit Ratio       | 94.7%               |
| Uptime          | 14d 6h 32m          |
+-----------------+---------------------+

wp apex-cache flush

Flush the cache. Optionally flush a specific cache group.

# Flush everything
wp apex-cache flush

# Flush a specific group
wp apex-cache flush --group=transients

# Flush on a specific multisite blog
wp apex-cache flush --url=sub.example.com

wp apex-cache diagnostics

Runs a comprehensive diagnostic check on the Redis connection, extension compatibility, and drop-in integrity.

$ wp apex-cache diagnostics

Running diagnostics...
 ✓ Redis connection: OK (0.4ms latency)
 ✓ PHP extension: phpredis 6.0.2
 ✓ Redis version: 7.2.3
 ✓ Drop-in file: intact (checksum match)
 ✓ Memory: 12.4 MB / 256 MB (4.8%)
 ✓ Eviction policy: allkeys-lru
 ✓ Persistence: RDB enabled
 
All 7 checks passed.

Hook	Fired When	Parameters
apex_cache_connected	Redis connection established	$client
apex_cache_flushed	Entire cache flushed	—
apex_cache_flush_group	A specific group is flushed	$group
apex_cache_error	A Redis error occurs	$exception

Example: Purge CDN after cache flush

add_action('apex_cache_flushed', function () {
    // Trigger CDN purge after WordPress cache is cleared
    wp_remote_post('https://api.cdn.example.com/purge', [
        'headers' => ['Authorization' => 'Bearer ' . CDN_API_KEY],
    ]);
});

Filter	Description	Parameters
apex_cache_key	Modify cache keys before storage	$key, $group
apex_cache_ttl	Override TTL for specific groups	$ttl, $group
apex_cache_ignored_groups	Modify the list of ignored groups	$groups
apex_cache_should_cache	Conditionally skip caching	$should, $key, $group
apex_cache_connection_params	Modify Redis connection parameters	$params

Example: Custom TTL per group

add_filter('apex_cache_ttl', function ($ttl, $group) {
    // Short TTL for transients, longer for options
    if ($group === 'transients') return 300;   // 5 minutes
    if ($group === 'options')    return 3600;  // 1 hour
    return $ttl;
}, 10, 2);

Example: Skip caching for specific keys

add_filter('apex_cache_should_cache', function ($should, $key, $group) {
    // Don't cache WooCommerce session data in Redis
    if ($group === 'wc_session_id') return false;
    return $should;
}, 10, 3);

Enable verbose logging to diagnose connection or performance issues:

define('APEX_REDIS_DEBUG', true);
define('APEX_REDIS_DEBUG_LOG', '/tmp/apex-cache-debug.log');

Log entries include timestamps, operation type, key, group, result (hit/miss), and latency in microseconds.

Redis Server Configuration

For optimal performance with WordPress object caching, we recommend these Redis settings:

# /etc/redis/redis.conf
maxmemory 256mb
maxmemory-policy allkeys-lru
save ""
appendonly no

• maxmemory-policy allkeys-lru — Evict least-recently-used keys when memory is full
• Disable persistence — Object cache data is ephemeral; persistence adds unnecessary I/O
• Set appropriate maxmemory — 256 MB handles most sites; increase for large multisite installs

WordPress Configuration

// Set a reasonable max TTL to prevent stale data
define('APEX_REDIS_MAXTTL', 86400); // 24 hours

// Ignore groups that don't benefit from caching
define('APEX_REDIS_IGNORED_GROUPS', [
    'counts', 'plugins', 'themes',
]);