Memcached is a popular open-source distributed memory caching system that can significantly improve the speed and scalability of your applications on Debian and AWS. It stores frequently accessed data in memory, reducing the need to fetch it from disk or database, and provides a simple and fast way to share data across multiple servers. Memcached is easy to install and configure, and can be used with a wide range of programming languages and frameworks. It is particularly well-suited for web applications that require fast and efficient access to frequently accessed data, such as session data, user profiles, and product catalogs.