Erlang

What is Erlang and OTP?

From Trapexit:

Erlang is a programming language used to build massively scalable soft real-time systems with requirements on high availability. Some of its uses are in telecoms, banking, e-commerce, computer telephony and instant messaging. Erlang’s runtime system has built-in support for concurrency, distribution and fault tolerance. Originally developed at Ericsson, it was released as open source in 1998.

OTP is set of Erlang libraries and design principles providing middle-ware to develop these systems. It includes its own distributed database, applications to interface towards other languages, debugging and release handling tools. These tools and applications distributed by Ericsson are complemented by numerous other open source projects.