Memcached

Memcached is a memory-based key-value store used to speed up dynamic web applications. It stores data and objects in system memory, reducing the need to access external databases or files. Memcached helps improve performance and reduce load on backend systems.

It is a general-purpose cache. Applications use it to store small chunks of data, such as results from database queries, API responses, session data, or page fragments. Its design focuses on simplicity, speed, and efficiency.

History and Background

Memcached was created in 2003 by Brad Fitzpatrick, who also founded LiveJournal. The goal was to reduce database load and improve response times. At the time, LiveJournal needed to serve many users while keeping costs low.

Traditional databases were too slow and overloaded under heavy traffic. Memcached helps by storing repeated query results in memory, so pages load faster.

Technical and adoption highlights:

• Originally written in Perl, then rewritten in C for:
  • Faster performance
  • Lower memory usage
• Quickly adopted by developers building large-scale web platforms
• Used by major websites, including:
  • Facebook
  • Twitter
  • YouTube
  • Reddit

Memcached is open source under the BSD license. It has no official corporate owner but is actively maintained by a community of contributors. Its simplicity, speed, and reliability have kept it in widespread use for more than 20 years.

Core Features and Functionality

Memcached is designed to be lightweight, fast, and easy to use. Its features reflect that goal.

• In-Memory Storage - Memcached stores all data in system memory. This reduces latency and allows near-instant reads and writes. Memory use is efficient and organized using a slab allocation system, which helps reduce fragmentation.
• Key-Value Model - Data in Memcached is stored as key-value pairs. Each item is assigned a string key and a value that can be text, numbers, or serialized objects. The value must be less than 1 megabyte.
  
  This model is simple and easy to integrate into applications. Most use cases involve caching frequently accessed or expensive-to-generate results.
• Time-to-Live (TTL) - Each item in Memcached has a TTL value. This controls how long it remains in memory. When the TTL expires, the item is removed. This helps keep the cache clean and up to date without manual intervention.
• LRU Eviction - Memcached uses a Least Recently Used (LRU) eviction policy. When the cache is full, it removes the oldest items that have not been accessed recently. This ensures memory is used for the most active data.
• Multi-threaded Support - Memcached supports multiple threads. It can handle concurrent requests from many clients at once. This allows it to scale with CPU resources and serve high-traffic sites.
• Stateless Design - Memcached does not store any data on disk. It does not track clients or requests. This makes it stateless. If the server restarts, the cache is empty. Applications must be able to fall back to the original data source if needed.
• Simple Protocol - Memcached uses a simple text-based protocol over TCP or UDP. It supports commands like get, set, delete, and flush. Many programming languages provide client libraries that wrap this protocol into simple function calls.

Advantages of Memcached

Memcached provides several clear benefits to developers and hosting environments.

• Speed - All operations happen in memory. This provides fast response times measured in microseconds. Pages load quicker, and systems feel more responsive under heavy use.
• Simplicity - Memcached has a small set of features and commands. It is easy to learn and integrate into applications. There are no complex configuration files or special rules.
• Scalability - Memcached is designed to scale out. You can add more servers to the cluster as demand grows. Each server manages its own keys. The application decides which server to contact based on a hash of the key.
• Low Overhead - Memcached uses few system resources. It runs as a single daemon and does not require other services. This makes it well-suited for shared hosting or containers.
• Wide Support - Memcached works with many languages and platforms. PHP, Python, Ruby, Java, and others all offer stable libraries. Hosting providers include Memcached in their managed services and control panels.

Limitations

While Memcached is fast and useful, it has some limits.

• No data persistence. If the server restarts, all cached data is lost.
• No support for complex data types. It stores only simple values.
• No built-in replication or clustering. Scaling relies on the client to distribute keys.
• Cache size is limited by available RAM.
• Not suitable for permanent storage or high-reliability use cases.

These limits make Memcached best for temporary, fast-access use.

Comparison with Other Tools

Before Memcached, developers relied on traditional database queries or file-based caching. These methods were slow and often created bottlenecks under load.

Memcached was one of the first widely used in-memory caches for web use. Unlike disk caching, Memcached stores data in RAM. This makes access times much faster. It uses a hash table to look up values quickly.

It predates Redis but shares a similar purpose. However, the two tools have key differences:

• Memcached only stores simple key-value pairs. Redis supports more data types.
• Memcached focuses on speed and simplicity. Redis includes features like persistence and replication.
• Memcached is often used for short-term, volatile caching. Redis can act as a cache and a datastore.

Memcached works well as a temporary cache layer but lacks some of the newer features found in more complex systems.

Memcached vs Redis

Redis has gained popularity as an alternative to Memcached. Both serve similar purposes but differ in design.

• Memcached is faster for simple string storage.
• Redis supports more data types and offers persistence.
• Memcached is easier to set up and uses less memory per item.
• Redis includes replication, scripting, and clustering.
• Memcached works best as a cache layer. Redis can act as both a cache and a datastore.

Choosing between them depends on the needs of the application.

Memcached Use Cases with NTC Hosting

Memcached is present in the majority of the web hosting plans offered by NTC Hosting. It’s also available with all servers (semi-dedicated, VPS, and dedicated servers) purchased with the Hepsia Control Panel. Using Memcached can significantly improve site performance. It supports many popular platforms and frameworks.

• Caching Database Queries - One of the most common uses is caching the result of expensive database queries. Applications check Memcached first. If the data is found, they skip the query. If not, they fetch it, store the result in Memcached, and return it. This reduces load on the database and speeds up page loads.
• Session Storage - Web applications use Memcached to store session data. Since it is fast and operates in memory, it allows quick session reads and updates. This helps maintain smooth performance for logged-in users.
• Object Caching - Frameworks like Django, Laravel, and Ruby on Rails include built-in support for Memcached. They use it to store view fragments, objects, or computed values that change infrequently.
• Content Management Systems - Popular CMS platforms such as WordPress, Drupal, and Joomla use Memcached to cache page components and database calls. This reduces load times and supports more concurrent visitors.
• High-Traffic APIs - APIs use Memcached to store repeated responses. This speeds up response times and reduces the need to perform the same calculations or lookups many times.