Maru
Elixir RESTful Framework
...Built-in support for namespacing and API versioning simplifies rolling changes or maintaining multiple client generations side by side. Error handling, helpers, and content negotiation are wired into the DSL, so common cross-cutting concerns are consistent across endpoints. Because Maru sits on Plug and Cowboy, it retains Elixir’s performance and concurrency while making API development fast and readable.