Have you ever wondered how websites like Facebook, YouTube, and Twitter handle millions of visitors every day without crashing? The answer lies in caching – and one of the most powerful caching technologies available is Memcached.
In this guide, we’ll explain what Memcached is, how it works, who uses it, and exactly how to enable it on your server.
What Is Memcached?
Memcached is an open-source, high-performance, distributed memory caching system. It was originally developed by Danga Interactive to speed up LiveJournal, and it’s now used by some of the biggest websites on the internet.
Why Do You Need Caching?
Every time a user requests a page or performs an action on your application, your server typically performs multiple database queries to retrieve data. Each database request adds load to your server. The more users you have, the more database queries are made, and the slower your application becomes.
This is where Memcached comes in.
Memcached reduces that load by storing frequently accessed data in dynamic memory (RAM) – think of it as short-term memory for your applications. Instead of fetching the same data from the database repeatedly, Memcached serves it directly from memory, which is significantly faster.
What Can Memcached Store?
Memcached stores key-value data for small, arbitrary strings or objects, including:
- ✅ Database query results
- ✅ API call responses
- ✅ Rendered page fragments
- ✅ Session data
- ✅ Any small, frequently accessed piece of data
How Memcached Works
Memcached operates using four main components that work together seamlessly:
| Component | What It Does |
|---|---|
| Client Software | An application that connects to Memcached servers using a given list of available servers |
| Client-Based Hashing Algorithm | Determines which Memcached server to use based on the cache “key” |
| Server Software | The actual Memcached server that stores values and their keys in an internal hash table |
| LRU (Least Recently Used) Eviction | When memory is full, this algorithm automatically removes the oldest or least-used data to make room for new data |
Simple Example of How It Works
- A user requests a piece of data (e.g., a user profile, a product list, or an API response).
- The application first checks Memcached to see if the data is already stored.
- If the data exists (cache hit), it’s returned instantly from memory – no database query needed.
- If the data doesn’t exist (cache miss), the application fetches it from the database, stores a copy in Memcached, and returns it to the user.
- The next time the same data is requested, it’s served directly from Memcached.
This architecture allows Memcached to be incredibly fast, scalable, and efficient – making it ideal for high-traffic environments.
Who Uses Memcached?
Memcached is battle-tested by some of the most popular websites on the planet:
| Platform | Monthly Visitors |
|---|---|
| YouTube | Billions |
| Billions | |
| Hundreds of millions | |
| Wikipedia | Billions |
| Hundreds of millions | |
| Hundreds of millions | |
| GitHub | Hundreds of millions |
It’s also supported by every major content management system (CMS) and framework, including:
- WordPress (via plugins like W3 Total Cache)
- Drupal (native support)
- Joomla (native support)
- Magento (for e-commerce)
- Laravel (native support)
- Ruby on Rails (native support)
- Django (native support)