Redis vs Memcached vs APCu: Best WordPress Object Cache

When optimizing your WordPress website for speed and performance, caching is a crucial aspect to consider. Object caching, in particular, can significantly reduce database load by storing the results of expensive queries so they can be quickly retrieved. The three most popular object caching solutions are Redis, Memcached, and APCu. Let’s break this down.

Redis: The Versatile In-Memory Data Store

Redis is an open-source, in-memory data structure store that serves as a database, cache, and message broker. Redis is highly versatile and capable of handling complex data types such as strings, lists, sets, and more. This flexibility allows it to be used for various tasks beyond simple caching, like session management, real-time analytics, and even full-blown databases.

Advantages:

• Persistence: Redis offers data persistence, meaning cached data can be saved to disk and restored, which is useful for critical data that can be lost if the server restarts.
• Advanced Data Structures: Redis supports complex data types, making it ideal for advanced caching scenarios.
• Horizontal Scalability: Redis can be scaled horizontally with Redis Cluster, allowing it to handle large workloads efficiently.
• Widely Supported: Many WordPress plugins and hosting providers offer built-in support for Redis, making it easy to implement.

Disadvantages:

• More Resource-Intensive: Redis is more resource-hungry compared to Memcached and APCu, requiring more memory and CPU.
• Setup Complexity: Configuring Redis can be more complex, particularly if you’re using advanced features like clustering.

Memcached: The High-Performance Key-Value Store

Memcached is another open-source, high-performance, distributed memory object caching system. It stores data in key-value pairs and is widely known for its simplicity and speed.

Advantages:

• Speed: Memcached is optimized for speed, making it an excellent choice for high-traffic sites where quick response times are critical.
• Low Resource Usage: Memcached is lightweight and uses minimal resources, which can be beneficial for servers with limited memory.
• Simplicity: It’s straightforward to set up and use, which makes it a popular choice for beginners and those looking for a hassle-free caching solution.

Disadvantages:

• No Persistence: Unlike Redis, Memcached doesn’t offer data persistence, so all cached data is lost if the server restarts.
• Limited to Simple Data Types: Memcached only supports simple key-value pairs, making it less versatile than Redis.
• Horizontal Scalability Challenges: Scaling Memcached horizontally can be more challenging than Redis, particularly if you need to maintain data consistency across nodes.

APCu: The Efficient Local Cache

APCu (Alternative PHP Cache User) is a single-server, in-memory caching solution designed to store PHP variables and data locally on a single server.

Advantages:

• Low Latency: Since APCu caches data locally on the same server, it provides extremely low latency, making it ideal for caching PHP objects and variables.
• Resource Efficiency: APCu is highly resource efficient making it suitable for environments with limited memory and CPU.
• Easy Setup: APCu is easy to install and configure, often requiring just a simple PHP extension.

Disadvantages:

• Single Server Limitation: APCu works only on a single server, so it’s not suitable for multi-server environments.
• No Advanced Features: APCu lacks the advanced features and data structure support that Redis offers.
• No Data Persistence: Like Memcached, APCu doesn’t offer data persistence, so all cached data is lost on server restarts.

Which One is Best for WordPress?

Choosing between Redis, Memcached, and APCu depends largely on your specific use case, server environment, and the demands of your WordPress site.

• Redis is the best choice if you need a versatile, scalable solution with data persistence and support for complex caching scenarios. It’s ideal for high-traffic sites that require robust caching and can handle the additional resource demands.
• Memcached is perfect for sites that need ultra-fast caching with minimal resource usage. It’s a great option for simple caching needs where the main priority is speed rather than persistence or advanced data structures.
• APCu is the best choice because caching PHP objects locally can dramatically improve performance. It’s particularly useful if you already have a distributed object cache like Redis or Memcached and want to complement it with a local cache.

Conclusion: Which is best for WordPress?

There’s no one-size-fits-all solution when it comes to object caching in WordPress. Redis, Memcached, and APCu each have their strengths and weaknesses. For 95% of WordPress websites, APCu cache is the best option because of end-user simplicity and effectiveness. Memcached is the second-best option because of its simplicity and ease easy of integration.