Redis Persistent Object Cache

Redis object caching stores expensive query results and computed objects in memory so WordPress does not repeat the same work on every request. It matters most for dynamic paths (logged-in sessions, cart/checkout, admin, search) where page cache is bypassed.

Object Cache vs Page Cache

Type	Scope	Works For	Limitation
Page Cache (LSCache, CDN)	Full HTML response	Anonymous users, static content	Logged-in users bypass it
Object Cache (Redis)	Database query results, objects, metadata	Logged-in users, WooCommerce carts, LMS sessions	Needs Redis server + proper config

How Redis Improves WordPress Performance

Action	Without Redis	With Redis	Benefit
Product Page Load	50+ queries run every request	Queries cached in memory	TTFB 100-300ms
Checkout Page	Queries hit DB directly	Cart/session data served from Redis	Stable checkout under load
Dashboard Access	DB hit for options/transients	Options pulled from Redis	Faster wp-admin

Implementation Steps

1. Install Redis on Ubuntu VPS:

   install-redis-ubuntu.sh

   sudo apt update
   sudo apt install -y redis-server

2. Enable Redis Persistence (RDB/AOF):

   Edit /etc/redis/redis.conf:

   redis.conf

   save 900 1
   save 300 10
   appendonly yes

   Restart Redis:

   restart-redis.sh

   sudo systemctl restart redis

3. Install WordPress Plugin:

   • Use Redis Object Cache plugin or LiteSpeeds built-in Redis connector.

4. Enable Object Cache:

   wp-redis-enable.sh

   wp redis enable

5. Verify Connection:

   wp-redis-status.sh

   wp redis status

Static vs Dynamic Strategy

Site Type	Redis Usage	Why
Static (Blogs)	Optional, minor gains	Mostly cached via page/CDN layers
Dynamic (WooCommerce, LMS, Membership)	Required, persistent cache ON	Handles cart, account, logged-in sessions efficiently

Best Practices

1. Run Redis on the same server unless scaling with high concurrency (then consider managed Redis).
2. Set a memory limit for Redis to avoid over-usage.
3. Use persistent mode (RDB + AOF) for reliability.
4. Flush Redis carefully; avoid doing it during peak hours.
5. Monitor Redis hit/miss ratio weekly.

Verification Steps

Check Redis plugin status:

wp-redis-status.sh

wp redis status

Expected Output:

wp-redis-status-output.txt

Status: Connected
Client: PhpRedis
Cache Hits: 12000
Cache Misses: 3000

Check via Redis CLI:

redis-info-stats.sh

redis-cli info stats | grep keyspace

Expected Output:

redis-info-stats-output.txt

keyspace_hits:15000
keyspace_misses:2500

Quick Lab

1. Install Redis on your VPS.
2. Enable persistence in /etc/redis/redis.conf.
3. Install the Redis Object Cache plugin.
4. Run wp redis enable to activate object cache.
5. Load your site, then check wp redis status.
6. Compare TTFB before and after enabling Redis.

Cheat Sheet (Redis Persistent Cache)

Task	Command
Install Redis	sudo apt install redis-server -y
Restart Redis	sudo systemctl restart redis
Enable Object Cache	wp redis enable
Flush Redis	wp redis flush
Check Status	wp redis status
Monitor Hits/Misses	redis-cli info stats

Expected Impact

With a properly configured persistent object cache, expect lower database load, steadier dynamic TTFB, and fewer performance collapses under concurrency.

What's Next

• Query Profiling Tools
• Backend Cleanup
• Offloading WordPress Search