Memcached operates as a distributed memory caching system, designed to improve the performance and scalability of web applications. Here's a simplified explanation of how Memcached works:

Client-Server Architecture : Memcached follows a client-server architecture. Client applications interact with Memcached servers over a network using a simple protocol.

In-Memory Data Storage : Memcached stores data in memory, which allows for extremely fast read and write operations. This data is organized as key-value pairs.

Caching Mechanism : When a client application needs to retrieve data, it first checks if the data is available in Memcached. If the data is found (a cache hit), it is quickly returned to the client. If the data is not found (a cache miss), the client fetches the data from the primary data source (such as a database) and stores it in Memcached for future access.

Key-Value Storage : Data in Memcached is stored using unique keys. Each key is associated with a corresponding value, which can be any arbitrary data such as strings, numbers, or serialized objects.
Hashing for Distribution : Memcached uses consistent hashing to distribute data across multiple servers in a cluster. This ensures that data is evenly distributed and allows for scalability by adding or removing servers dynamically without affecting the overall system.

Expiration and Eviction : Memcached supports setting expiration times for cached data. After the expiration time elapses, the data is automatically evicted from the cache. Additionally, Memcached employs an LRU (Least Recently Used) eviction policy to remove least recently accessed data when memory is full.

Client Libraries : Memcached provides client libraries for various programming languages, allowing developers to easily integrate caching functionality into their applications. These libraries handle communication with Memcached servers and provide simple APIs for storing and retrieving data.