Varnish

Varnish Cache is a web application accelerator also famous as a caching HTTP reverse proxy. You can install it in front of any server that speaks HTTP and configure it to cache the contents. Varnish Cache is really, really fast and will increase the speed of your website. One of the essential virtues of Varnish Cache is the flexibility of its domain-specific language, VCL, which allows you to choose how incoming requests should be tackled.

Memcached

Memcached is a general-purpose distributed memory object caching system for increasing the loading speed of dynamic database-driven sites. It is used to decrease the number of times an external data source (such as a DB or API) is read by caching data and objects in RAM. The Memcached distributed memory object caching system uses a client/server architecture. The Memcached distributed memory caching system is used by some of the most popular web sites on the Internet and is supported by popular web apps like Joomla and WordPress.

Node.js

Node.js is a software platform for writing highly scalable Internet apps. Built on Chrome's JavaScript runtime, Node.js uses an event-driven, asynchronous input/output model that makes it lightweight and effective, suitable for real-time content-intensive Internet applications. Node.js uses Google's V8 JavaScript engine, libUV, and several in-built libraries.