Memcached - The Ultimate Beginner's Guide

April 30, 2023

Memcached - The Ultimate Beginner's Guide


In today's fast-paced web development, it's essential to have tools that help with scaling and optimizing application performance. This is where Memcached, a high-performance distributed caching system, comes into play.

What Is Memcached?

Memcached is an open-source, high-performance, distributed memory object caching system. It is commonly used to speed up dynamic web applications by alleviating database load. Memcached was designed to be a fast and efficient caching solution that can reduce the amount of time it takes for a website or application to retrieve data from a database.

Memcached stores data in the server’s RAM, which allows for very fast access times. This makes it an ideal choice for applications that need to store and retrieve large amounts of data quickly.

Importance of Memcached in Modern Applications

In modern web development, performance is everything. Users expect websites and applications to load quickly, and any delay can result in lost revenue or decreased engagement. This is where Memcached comes in – by caching frequently accessed data in memory, Memcached can significantly speed up database queries and improve overall application performance.

Memcached is also highly scalable, which makes it a popular choice for large-scale applications that need to handle heavy traffic loads. It can be deployed across multiple servers, allowing for efficient distribution of cached data and ensuring that performance remains consistent even under heavy load.

With its ability to improve performance, scalability, and availability, Memcached has become an essential tool for many developers and organizations.

History of Memcached

Founding of Memcached

Memcached was created in 2003 by Brad Fitzpatrick while working at LiveJournal. Fitzpatrick needed a way to improve performance on the site, which at the time was struggling with slow database queries. He developed Memcached as a caching layer to sit between the database and the web application, allowing frequently accessed data to be stored in memory and retrieved quickly.

Evolution of Memcached over the Years

Since its founding, Memcached has undergone numerous changes and updates. In 2007, Facebook released a modified version of Memcached called "mcrouter" which added support for sharding and other features. Later, Twitter created "twemcache," a fork of Memcached with additional scalability features.

Today, Memcached is widely used in the industry and has become an integral part of many web development stacks. It continues to be developed and maintained by a dedicated community of developers, ensuring that it remains a viable and reliable solution for improving application performance.

Overall, Memcached's history demonstrates its importance in modern web development, as well as its ability to evolve and adapt over time to meet the needs of the industry.

Benefits of Memcached

Improved Application Performance

By caching frequently accessed data in memory, Memcached reduces the load on backend servers and improves application performance. This means that web pages and APIs can be served faster, resulting in a better user experience.


Memcached is designed to be highly scalable and can handle large amounts of data across multiple servers. This makes it suitable for use in large-scale web applications where high availability and fault tolerance are critical.

Reduced Database Load

By caching frequently accessed data in memory, Memcached reduces the number of queries made to a database, which can help reduce the load on the database server. This can result in reduced latency, faster response times, and improved scalability.

Distributed Caching

Memcached uses a distributed architecture, which means that cached data is stored across multiple servers. This provides redundancy and fault tolerance, as well as improved performance by allowing data to be cached closer to the application server.

Simple API

Memcached provides a simple API for storing and retrieving data from the cache. The API supports key-value pairs, with keys being strings and values being any serializable object. Here's an example of how to store and retrieve data using the Python client:

import memcache

# Connect to Memcached Server

mc = memcache.Client(['localhost:11211'])

# Store a Value in the Cache

mc.set('my_key', 'my_value')

# Retrieve a Value From the Cache

result = mc.get('my_key')
print(result) # Output: 'my_value'


Memcached is open source and free to use, which makes it a cost-effective solution for caching frequently accessed data in web applications. Additionally, because it reduces the load on backend servers, it can help reduce infrastructure costs by allowing servers to handle more traffic.

Key Features of Memcached

In-Memory Data Storage

One of the primary features of Memcached is its in-memory data storage. This means that it stores data in RAM instead of on disk, so it can access data much faster than traditional databases. Since data is stored in RAM, it allows for lightning-fast data access and retrieval.

Distributed Architecture

Another significant feature of Memcached is its distributed architecture. It allows multiple servers to work together as a single entity. This means that you can add more servers to scale up your infrastructure as needed. Additionally, if one server fails, other servers can continue to serve requests, ensuring high availability.

Cache Expiration and Eviction

Memcached offers the ability to set expiration times for cached data. You can specify how long you want the data to be cached before it is automatically removed from the cache. This helps to keep the cache fresh and ensures that stale data is not used. Memcached also uses an eviction algorithm to remove data when the cache is full, ensuring that the most recently used data is kept in the cache.

Multi-Language Support

Memcached has support for multiple programming languages, including PHP, Python, Ruby, Java, and C#. This makes it a versatile tool that can be used in various environments. Also, it provides a consistent API that can be used across different programming languages, making it easy to integrate with your application.

High Performance and Scalability

Memcached is designed to handle high traffic websites and applications. With its in-memory caching architecture and distributed nature, it can handle large amounts of data and requests without any significant performance degradation. Additionally, it can scale horizontally by adding more servers to the infrastructure.

Simple and Lightweight

Memcached is simple to use and lightweight compared to other caching solutions. It has a small memory footprint and does not require complex configurations or installations. It can be quickly set up and integrated into your application, making it an ideal choice for developers who need a fast and easy-to-use caching system.

In conclusion, Memcached offers several features that make it an excellent choice for developers looking for a high-performance caching solution. Its in-memory data storage, distributed architecture, cache expiration and eviction, multi-language support, high performance and scalability, and simplicity make it a versatile tool that can help speed up dynamic web applications.

Use Cases for Memcached

Caching Web Pages

One of the primary use cases for Memcached is caching web pages. When a user visits a website, the server generates the HTML code for the page dynamically. This can be a slow process, especially if the website is complex or receives a lot of traffic. By using Memcached to cache the HTML code, the server can quickly retrieve the pre-generated HTML for frequently accessed pages, thereby reducing load times and improving overall performance.

Here's an example of how you might use Memcached to cache a web page in PHP:

$cache = new Memcached();
$cache->addServer('localhost', 11211);

$key = 'my-web-page';
$html = $cache->get($key);

if (!$html) {
// Generate the HTML for the page here
$html = generate_html();

// Cache the HTML for future requests
$cache->set($key, $html, 3600); // Expire after 1 hour

echo $html;

Storing Session Data

Another common use case for Memcached is storing session data. When a user logs in to a website, the server creates a session and stores information about the user (such as their username and preferences). By using Memcached to store this session data in memory, the server can quickly retrieve it on subsequent requests, rather than having to look it up in a database or file system.

Here's an example of how you might use Memcached to store session data in Node.js:

const memcached = require("memcached");

const client = new memcached("localhost:11211");

    secret: "my-secret-key",
    resave: false,
    saveUninitialized: true,
    cookie: {
      secure: true,
    store: {
      get: function (sid, cb) {
        client.get(sid, cb);
      set: function (sid, session, cb) {
        client.set(sid, session, 3600, cb); // Expire after 1 hour
      destroy: function (sid, cb) {
        client.del(sid, cb);

Speeding Up Database Queries

Memcached can also be used to speed up database queries by caching the results. When a query is executed, the server checks if the result is already stored in Memcached. If so, it returns the cached result rather than executing the query again. This can significantly reduce the load on the database and improve overall performance.

Here's an example of how you might use Memcached to cache the results of a MySQL query in Python:

import memcache
import MySQLdb

# Connect to Memcached

cache = memcache.Client(['localhost:11211'])

# Connect to MySQL

db = MySQLdb.connect(host='localhost', user='myuser', passwd='mypassword', db='mydb')

cursor = db.cursor()

# Execute the Query

query = "SELECT * FROM mytable WHERE column = %s"
params = ('myvalue',)
key = 'my-cached-result'
result = cache.get(key)

if not result:
cursor.execute(query, params)
result = cursor.fetchall()

# Cache the Result for Future Requests

cache.set(key, result, 3600) # Expire after 1 hour

# Use the Cached Result

for row in result:

Getting Started with Memcached

Installation and Setup

Installing Memcached is a straightforward process. You can install it on Unix-based systems like Linux or macOS using package managers like apt-get or yum. Windows users can download and install a pre-compiled binary from the official website. Once you've installed Memcached, you can start the daemon using the following command:

memcached -d -m -p

The -d flag tells Memcached to run as a daemon or background process, while -m specifies the amount of memory in megabytes allocated for caching. The -p flag specifies the port number on which Memcached listens for incoming requests from clients.

Basic Commands and Data Types

Memcached uses a simple key-value store data model. Data is stored in the form of key-value pairs, where keys are unique identifiers and values are any serializable data type like strings, numbers, or objects. Here are some basic commands for working with Memcached:

  • set: Stores a key-value pair in Memcached
  • get: Retrieves a value from Memcached using its key
  • delete: Removes a key-value pair from Memcached
  • flush_all: Clears all entries from Memcached

Memcached supports various data types, including strings, integers, booleans, and arrays. To store multiple values for a single key, you can use an array or object. For example:

// Storing a string
memcached.set("name", "Alice");

// Storing an integer
memcached.set("age", 25);

// Storing an array
memcached.set("fruits", ["apple", "banana", "kiwi"]);

// Storing an object
memcached.set("person", { name: "Bob", age: 30 });

Best Practices for Memcached

Here are some best practices to follow when working with Memcached:

  • Use meaningful and descriptive keys to make it easier to retrieve data.
  • Set a reasonable expiration time for cached data to avoid stale data.
  • Avoid overloading the cache by storing large objects or data that is rarely accessed.
  • Monitor Memcached server metrics like memory usage, hit rate, and evictions to optimize performance.

Language Support

Memcached supports many programming languages, including Java, Python, Ruby, PHP, and Node.js. You can use Memcached client libraries specific to your language to interact with Memcached servers.

Here's how you can use the Memcached client library in Node.js:

const memcached = require("memcached");

const client = new memcached("localhost:11211");

client.set("name", "Alice", 10, (err) => {
  if (err) throw err;

  client.get("name", (err, value) => {
    if (err) throw err;

    // Output: Alice

Integrating with Other Databases

Memcached can be used as a caching layer to improve the performance of other databases like MySQL, PostgreSQL, and MongoDB. By caching frequently accessed data in Memcached, you can reduce the number of queries sent to the database, resulting in faster application response times.

To integrate Memcached with MySQL, for example, you can use a MySQL Memcached plugin like mysqld_memcached. The plugin automatically caches query results in Memcached, reducing the number of database queries.

Memcached in Production

Scaling Memcached

Scaling Memcached involves adding more nodes to increase the capacity and throughput of the cache. To scale Memcached, you can use either the horizontal or vertical scaling approach.

Horizontal scaling involves adding more nodes to the Memcached cluster, while vertical scaling involves increasing the resources (such as CPU, RAM) of each node in the cluster.

To add more nodes to the Memcached cluster, you need to ensure that all nodes are configured with the same configuration parameters like port, memory size, and connection limit. You can achieve this by using containerization technologies like Docker or Kubernetes to deploy and manage Memcached instances.

Here's an example of how to start a Memcached instance with Docker:

docker run -d --name memcached -p 11211:11211 memcached:latest

In addition to horizontal scaling, you can also scale Memcached vertically by increasing the resources allocated to each Memcached instance. This can be done by adjusting the memory limit parameter in the Memcached configuration file. For example:

-m 1024

This sets the maximum memory size of the Memcached instance to 1GB.

High Availability

High availability is essential for production environments to ensure continuous operation in case of failures. One way to achieve high availability for Memcached is by using a clustering solution like Memcached Cloud or Elasticache.

These services provide automatic replication and failover capabilities, allowing you to maintain a highly available Memcached cluster without worrying about manual failover processes.

Another way to achieve high availability is by manually configuring failover between multiple Memcached instances. This can be done by using a client library like libmemcached, which provides automatic failover support.

Monitoring and Troubleshooting

Monitoring and troubleshooting Memcached involves tracking metrics like hit/miss ratios, memory usage, and connection counts. You can use tools like Munin or Nagios to monitor Memcached instances and alert you in case of anomalies.

To troubleshoot issues with Memcached, you can use the memcached-tool utility that comes with the Memcached package. This tool provides detailed statistics on connections, evictions, and general cache usage.

memcached-tool :11211 stats

This command shows the current statistics of a Memcached instance running on ``.

In conclusion, by following these best practices, you can ensure that Memcached is deployed, scaled, and maintained correctly in production environments.

Future of Memcached

Memcached is a mature technology, but its developers are still working on enhancing it. One of the significant changes to expect in the future is the adoption of Memcached version 2.0. The new version will come with several improvements that seek to make the tool more reliable, efficient, and easier to use.

One of the critical enhancements in Memcached 2.0 is the introduction of advanced data structures. Currently, Memcached only supports basic data types such as strings, integers, and booleans. However, version 2.0 will introduce more complex data structures such as lists, sets, and maps. These structures will allow developers to store and manipulate structured data more efficiently, eliminating the need to serialize and deserialize data before caching.

Memcached 2.0 will also include support for binary protocols. Unlike the current text protocol, binary protocols transmit data in binary format, which makes them faster and more efficient. Binary protocols also support features such as pipelining and batching, which can improve performance and reduce network overhead.

Another exciting development in Memcached's future is the integration of other technologies such as machine learning and artificial intelligence. With the rise of big data and IoT, there is a need to process vast amounts of data quickly and efficiently. Memcached's ability to cache data in-memory makes it an ideal candidate for applications that require real-time processing. By integrating machine learning and AI, Memcached can help developers build intelligent applications that learn from user behavior and adapt to changing circumstances.

Overall, the future of Memcached looks promising, with developers working on adding new features and improving existing ones. As a developer, it's essential to keep up with these developments and explore how they can benefit your applications.


To sum it up, Memcached is a powerful and efficient tool that can help improve the performance of your web applications. As a beginner, understanding its basic concepts and functionalities can go a long way in utilizing its full potential. With this ultimate guide, you now have a solid foundation to start using Memcached for your caching needs.

Frequently Asked Questions

What is the use of Memcached?

Memcached can greatly improve web application performance, particularly for read-heavy applications, by caching commonly-used data such as session data, user profiles, and product information. It's widely used by large, high-traffic websites such as Facebook, Twitter, and YouTube.

Is Memcached in SQL?

Memcached is not a relational database like SQL, but an open-source distributed memory caching system used to speed up dynamic web applications by reducing the number of times data needs to be retrieved from a database. It stores frequently accessed data in memory, which makes it faster to access than if it were stored on disk. In contrast, SQL is used for storing and retrieving structured data in a relational database.

What is the difference between Memcached and file system cache?

Memcached and file system cache are two caching mechanisms used to enhance web application performance. File system cache stores frequently accessed data in the server's file system, while Memcached stores frequently accessed data in the server's RAM. File system cache is suitable for storing static files such as images, CSS, and JavaScript files. Memcached is more appropriate for storing dynamic data that requires fast retrieval.

What is the difference between memcache and Redis?

Memcache and Redis are both used for caching, but they differ in functionality. Memcache focuses on key-value pair caching while Redis offers more advanced features such as built-in support for data structures like lists, sets, and hashes, persistence to disk, scalability, replication, and high availability. Redis also supports a wider range of programming languages than memcache.

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