Redis vs. Memcached WordPress: Which one to pick?
To improve your WordPress site performance, you need caching. It reduces the load on your WordPress hosting servers. As a result, your website runs faster.
Both Redis and Memcached offer caching capabilities. They have a lot of similarities. For a suitable WordPress cache, you need to consider the differences between Redis and Memcached.
In this article, we will compare Redis vs. Memcached. We will use factors such as scaling, storage, and more features.
Object caching in WordPress
Object caching is a process that stores database query results. You can then retrieve them quickly when needed. The cached object is served directly from the cache. There is no need to query the database.
WordPress is a CMS that relies on databases to store and retrieve data. A large number of database queries can flood the server with requests.
The database server gets overloaded. As a result, you get a slow site speed.
Object caching eases the server load. It offers faster web pages.
You could use a caching plugin such as W3 Total Cache. It is configured to manage WordPress caching.
Overview of Redis
Redis is an open-source, in-memory data structure store. It is used as a database, cache, and message broker.
Redis stores data in memory instead of a disk or SSD. Due to this, it delivers high performance.
It offers built-in replication. You can place data closer to the user’s location for the lowest latency.
Redis was initially created in 2009 by Salvatore Sanfilippo. He used to improve a web log analyzer.
The prototype was written in Tcl and later translated to C language.
Some of the Redis features include:
- Redis Persistence
- Built-in Lua scripting
- Supports many data types
- Redis Pub/Sub (Publish and Subscribe)
- Geospatial support
- Redis Cluster
- Redis Sentinel
Overview of Memcached
Memcached is an open-source, distributed memory caching system.
It is used to cache database, API calls, and page rendering. It helps improve the application speed. Memcached reduces the database load. So you get a fast page loading time.
Memcached was initially created in 2003 by Brad Fitzpatrick. He used it for his website LiveJournal. It was first developed in the Perl language and then translated into C.
Memcached is used by companies such as:
Similarities between Redis & Memcached
Redis and Memcached have many similar features. Some of them include:
- NoSQL, in-memory data structures
- Improves application speed
- Sub millisecond latency
- Data partitioning
- Ease of use for developers
Both Redis and Memcached offer millisecond response times. They can read data faster than disk-based databases.
You also get data partitioning. You can spread data on many nodes. It helps to handle data when your traffic increases.
Redis vs. Memcached Comparison
1. Scaling and Architecture
Redis has a single-threaded architecture. It offers horizontal scaling. It also has native cluster support.
Redis clusters use a master/slave architecture. Every master node has two slave nodes. It helps with redundancy.
If the master node fails, then one of the slave nodes is used as the new master. However, this can cause more complexity. You would need to maintain many nodes.
The Redis Enterprise version offers an enterprise-grade cluster. It is used for multiple Redis databases.
Memcached is multi-threaded and scales vertically. The only requirements are to give it more cores and memory.
It can make use of many processing cores. You can take care of more operations. All you need is to scale up the capacity.
You don’t have to spread data across nodes. You can have horizontal scaling by adding more nodes. The data is then spread on the client level. This method is more complex to perform.
Both Redis and Memcached support languages such as:
- C, C++
Memcached supports fewer languages than Redis. It does use all the popular languages.
Redis offers many data types and data structures:
- Sorted Set
- Binary safe data
- Bit arrays
The data structures provided by Radis allow more flexibility for large datasets. You can filter cache contents from wp-config.php core WordPress server files.
Memcached server offers no data types. It supports plain binary strings for read-only data. Memcached is preferred for use cases that need less memory.
Redis uses persistent disk storage. It is used to combat outages and network failure. It offers data persistence using Snapshots. With snapshots, you can store point-in-time datasets on a disk. It is helpful for disaster recovery.
Redis supports two persistence methods:
- Redis Database Backup (RDB) persistence
- Append Only File (AOF) persistence
Redis helps take regular snapshots of data. You can configure Redis to create database backups manually or automatically.
Redis also allows Append Only File log. It keeps a record of the executed commands and data changes. You can re-run the commands to restore a dataset.
Memcached does not support disk data persistence. You may lose the data after rebooting.
Replication is the process of creating copies of data from one server to another. Redis offers a leader/follower (master-slave) replication. It creates exact copies of the master instances.
If there is a disconnect, the replica automatically reconnects to the master node. The replica will execute partial re-syncs. It will only copy the data that was missed during the disconnection.
For high availability, Redis offers Redis Sentinels. It helps prevent failures. Memcached does not support replication without third-party software. You can use an open-source tool such as Repcached for high availability.
5. Cache Eviction Policies
Redis supports many types of eviction policies. Some of which include:
|no eviction||Returns an error if the memory limit has been reached.|
|allkeys-lru||Evicts the least recently used keys. Lru stands for least recently used.|
|allkeys-lfu||Evicts the least frequently used keys out of all keys. Lfu stands for least frequently used.|
|allkeys-random||Randomly evicts keys or data out of all keys|
|volatile lru||Evicts the least recently used keys with an expiration fieldset.|
|volatile-lfu||Evicts the least frequently used keys that have an expiration fieldset|
|volatile random||Randomly evicts keys that have an expiration fieldset.|
|volatile-ttl||Evicts the shortest time to live data with an “expire” fieldset.|
Memcached only offers LRU (least recently used) eviction policy.
Which is better: Redis or Memcached
When deciding what cache to use for WordPress, you need to see your requirements.
Redis is flexible and offers richer functionality. It is also more cost-efficient at scale. Redis provides more data types. You can have better data operations.
You also get additional features such as real-time geospatial support. If you work with location apps, Redis is a good option. Redis is also the better choice if you need persistence, replication, and advanced features.
Memcached offers simplicity and ease of use for caching. It is multi-threaded and offers better scaling. If you are working with one data type and don’t need persistence, Memcached is a good option.
Memcached and Redis offer NoSQL data management solutions. Both are based on a key-value store data model. They store data in RAM. Data stores are also quite similar. Both offer caching features for low latency.
For simple applications with a single data type, Memcached is a good option. Redis is preferred if you work with complex data-type operations. Redis offers more functionalities and useful commands for keys.
Both the solutions add a functional caching layer for your website.
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