Storage Backends

MilliCache works with any Redis-compatible server. This guide covers supported backends, configuration, and recommendations.

Supported Backends#

Backend License Key Feature Best For
Redis RSALv2 Most popular, proven Most deployments
ValKey BSD-3 Open-source Redis fork License-concerned users
KeyDB BSD-3 Multithreaded High-throughput needs
Dragonfly BSL Memory efficient Large cache requirements

All backends use the same protocol and configuration. Your choice depends on licensing preferences, performance needs, and hosting availability.

Quick Comparison#

Redis#

The original in-memory data store. Most documentation, hosting support, and community resources.

  • Pros: Battle-tested, extensive documentation, widest hosting support
  • Cons: RSALv2 license may concern some users
  • Install: redis.io/docs/install

ValKey#

Linux Foundation fork of Redis, fully open-source under BSD-3 license.

  • Pros: Fully open-source, active development, drop-in Redis replacement
  • Cons: Newer project, less hosting support currently
  • Install: valkey.io/docs

KeyDB#

Multithreaded Redis fork with improved performance on multi-core systems.

  • Pros: Higher throughput, MVCC for better concurrency
  • Cons: Less widespread than Redis
  • Install: docs.keydb.dev

Dragonfly#

Modern Redis alternative with significantly better memory efficiency.

  • Pros: Uses less memory for same data, faster on large datasets
  • Cons: Newer, Business Source License
  • Install: dragonflydb.io/docs

MilliCache Configuration#

Connection settings are the same for all backends.

Basic Connection#

 1// wp-config.php
 2define( 'WP_CACHE', true );
 3
 4define( 'MC_STORAGE_HOST', '127.0.0.1' );
 5define( 'MC_STORAGE_PORT', 6379 );

With Authentication#

 1define( 'MC_STORAGE_HOST', 'redis.example.com' );
 2define( 'MC_STORAGE_PORT', 6379 );
 3define( 'MC_STORAGE_PASSWORD', 'your-password' );

Using Unix Socket#

 1define( 'MC_STORAGE_HOST', '/var/run/redis/redis.sock' );
 2define( 'MC_STORAGE_PORT', 0 );  // Ignored for sockets

With TLS (e.g. AWS ElastiCache)#

 1define( 'MC_STORAGE_HOST', 'tls://master.example.cache.amazonaws.com' );
 2define( 'MC_STORAGE_PORT', 6379 );

Multiple Sites on Same Server#

Use different databases or prefixes:

 1// Site A
 2define( 'MC_STORAGE_DB', 0 );
 3define( 'MC_STORAGE_PREFIX', 'sitea' );
 4
 5// Site B
 6define( 'MC_STORAGE_DB', 1 );
 7define( 'MC_STORAGE_PREFIX', 'siteb' );

All Connection Constants#

Constant Default Description
MC_STORAGE_HOST 127.0.0.1 Hostname, IP, socket, or tls://host
MC_STORAGE_PORT 6379 TCP port (0 for sockets)
MC_STORAGE_PASSWORD '' AUTH password
MC_STORAGE_DB 0 Database number (0-15)
MC_STORAGE_PERSISTENT true Use persistent connections
MC_STORAGE_PREFIX mll Key prefix

These settings are recommended for WordPress caching workloads:

 1# Memory allocation (adjust based on your needs)
 2maxmemory 256mb
 3maxmemory-policy allkeys-lru
 4
 5# Persistence (optional - cache can be regenerated)
 6save ""
 7appendonly no
 8
 9# Performance
10tcp-keepalive 300
11timeout 0
12
13# Security (if exposed to network)
14bind 127.0.0.1
15requirepass your-strong-password

Memory Sizing#

Site Size Recommended Memory
Small (< 100 pages) 64 MB
Medium (100-1000 pages) 128-256 MB
Large (1000+ pages) 512 MB+

The allkeys-lru eviction policy automatically removes least-recently-used entries when memory is full.

Testing Your Connection#

After configuration, verify the connection:

 1# Quick test
 2wp millicache test
 3
 4# Check status
 5wp millicache status
 6
 7# View stats
 8wp millicache stats

Troubleshooting Connection Issues#

Connection Refused#

Error: Connection refused

Causes:

  • Server not running
  • Wrong host/port
  • Firewall blocking connection

Solutions:

 1# Check if Redis is running
 2redis-cli ping
 3
 4# Check listening port
 5netstat -tlnp | grep 6379
 6
 7# Test connection manually
 8redis-cli -h 127.0.0.1 -p 6379 ping

Authentication Failed#

Error: NOAUTH Authentication required

Solution: Set the password constant:

 1define( 'MC_STORAGE_PASSWORD', 'your-password' );

Timeout#

Error: Connection timed out

Causes:

  • Server overloaded
  • Network issues
  • Firewall timeout

Solutions:

  • Check server resources
  • Verify network connectivity
  • Check firewall rules

Cloud Provider Options#

Most cloud providers offer managed Redis:

Provider Service
AWS ElastiCache for Redis
Google Cloud Memorystore
Azure Azure Cache for Redis
DigitalOcean Managed Redis
Upstash Serverless Redis

For managed services, use the provided connection details in your MilliCache configuration.

Performance Tips#

  1. Run locally when possible — Same-machine Redis has lowest latency
  2. Use persistent connections — Reduces connection overhead
  3. Enable compression — MC_CACHE_GZIP reduces network transfer
  4. Size memory appropriately — Avoid frequent evictions
  5. Monitor with wp millicache stats — Track cache efficiency

Next Steps#