Use Redis for most WordPress database cache jobs. Pick Memcached when you want a tiny, simple cache and you do not care if it forgets everything after a restart. WordPress has a built-in object cache API, but it only lasts for one page load unless you add a persistent cache backend like Redis or Memcached [source: WordPress].
TLDR: Redis is usually the better choice for WordPress sites with WooCommerce, memberships, search, filters, or lots of logged-in users. Memcached is great for simple sites that just need fast temporary storage. Example: a store doing 50,000 page views per day may cut repeat database queries by 70% after adding Redis object cache, which can make admin pages and product pages feel much snappier. If your host offers both, start with Redis.
Contents
- 1 What is database caching in WordPress?
- 2 Redis in plain English
- 3 Memcached in plain English
- 4 Redis vs Memcached: the quick fight card
- 5 When Redis is the better pick
- 6 When Memcached is the better pick
- 7 Will caching replace good hosting?
- 8 What about page cache?
- 9 Simple setup checklist
- 10 Which one should you choose?
What is database caching in WordPress?
WordPress asks the database questions all day.
“What is this product?”
“Who is this user?”
“Which posts match this search?”
“Does this coupon still work?”
That gets old fast.
A database cache saves the answers in memory. Memory is much faster than MySQL or MariaDB disk work. So WordPress can grab the saved answer instead of asking the database again.
In WordPress, this is usually called persistent object caching. It stores common things like options, posts, users, terms, menus, and query results.
Think of it like a sticky note on your monitor. The database is the filing cabinet across the room. Sticky note wins.
Redis in plain English
Redis is an in-memory data store. That means it keeps data in RAM. It is fast. Very fast.
Redis can store simple values. It can also store richer stuff, like lists, hashes, sets, and sorted sets. For WordPress, that makes it flexible.
Redis can also write data to disk. So if the server restarts, Redis can often restore cached data. That is not always needed for cache, but it is nice. It avoids the “cold cache” grumble after every restart.
Honestly, it feels like Redis was built for the kind of messy site WordPress becomes after plugins move in and start throwing shoes everywhere.
Memcached in plain English
Memcached is also an in-memory cache. It is older. It is simple. It does one job well.
It stores key-value pairs. WordPress says, “Here is a key.” Memcached says, “Here is the saved data.” Done.
Memcached does not try to be fancy. It does not persist data to disk by default. Restart it, and the cache is gone. That is fine for many sites. Cache can be rebuilt.
Memcached is like a whiteboard. Fast to read. Easy to wipe. Sometimes too easy.
Redis vs Memcached: the quick fight card
- Speed: Both are fast. For normal WordPress use, the difference is often small.
- Features: Redis wins. It has richer data tools.
- Simplicity: Memcached wins. It is lean and boring, which can be good.
- Persistence: Redis wins. It can save data to disk.
- Memory control: Both can evict old items when memory fills.
- WordPress plugin support: Redis usually feels smoother today.
- Scaling: Both can work across servers, but setup matters.
When Redis is the better pick
Choose Redis if your site does more than show static blog posts.
It shines for:
- WooCommerce stores with carts, orders, stock checks, and filters.
- Membership sites with lots of logged-in users.
- Learning sites with course progress and dashboards.
- News sites with heavy archives and search.
- Large admin panels that currently feel like walking through mud.
The catch is that Redis needs good setup. Bad settings can cause weird cache growth. It drives me crazy when a site is “optimized” but Redis has no memory limit. Then everyone acts shocked when the server starts sweating.
Use a memory cap. Use proper eviction rules. Monitor it.
For WordPress, many site owners use the Redis Object Cache plugin. Hosts may also include Redis at the server level. Some managed WordPress hosts turn it on with one switch.
When Memcached is the better pick
Choose Memcached if you want simple caching with low fuss.
It is a good fit for:
- Content sites with many repeat visitors.
- Small business sites that need a quick speed boost.
- Older hosting setups where Memcached is already installed.
- Teams that want fewer settings to break.
Memcached is not dumb. It is focused. That is its charm.
The annoying bit? If it restarts, every cached object disappears. Your site still works. But the database gets busy for a while. On a small site, who cares. On a busy store during a sale, that can mean pages take 2 seconds longer until the cache warms back up.
Will caching replace good hosting?
Nope.
Cache helps. It does not fix a terrible server, a bloated theme, or 48 plugins fighting in a trench coat.
If your database is slow because tables are huge, indexes are missing, or plugin queries are awful, Redis and Memcached can hide some pain. They do not cure it.
Still, object caching is often one of the best wins for database-driven WordPress sites. WordPress.org recommends persistent object caching for sites that reuse expensive query results often [source: WordPress Hosting Handbook].
What about page cache?
Page cache and database cache are not the same thing.
Page cache saves the final HTML page. It is great for visitors who are not logged in.
Database cache saves pieces of data used to build pages. It helps more when pages cannot be fully cached.
That matters for:
- Carts
- Checkout
- Account pages
- Dashboards
- Search results
- Filtered product pages
A blog can be fine with page cache alone. A store needs more help.
Simple setup checklist
- Ask your host if Redis or Memcached is available.
- Install the right object cache plugin or enable the host feature.
- Turn on persistent object cache in WordPress.
- Set a memory limit for Redis or Memcached.
- Test before and after with real pages.
- Watch database queries using Query Monitor or host tools.
- Check admin speed, not just the homepage.
Do not test only your front page. That can lie to your face.
Test product filters. Test checkout. Test account pages. Test wp-admin. Test search. That is where object caching earns its snacks.
Which one should you choose?
For most modern WordPress sites, choose Redis.
It has better features. It works well with complex sites. It is widely supported by managed WordPress hosts. It is a strong pick for WooCommerce and membership sites.
Choose Memcached if your setup already supports it, your site is simpler, and you want a small cache layer with fewer knobs.
Here is the simplest rule:
- Blog or brochure site? Memcached is fine. Redis is also fine.
- WooCommerce or logged-in users? Pick Redis.
- High traffic with heavy queries? Pick Redis and monitor it.
- Old server with Memcached ready? Use it rather than using nothing.
The worst choice is no persistent object cache on a busy database-driven site.
Redis is the fancy cooler with compartments. Memcached is the plain cooler full of ice. Both keep things fresh. Redis just handles the picnic chaos better.
