Janus
Janus is a statically-typed programming language designed for creating highly concurrent and parallel programs, with built-in constructs for modern software engineering techniques. Its main uses include developing scalable and efficient applications that require concurrent execution, such as distributed systems, web servers, and high-performance computing.
Popularity: Less than 1% of developers are using or have used this language.*
*According to StackOverflow's 2023 survey.