RapidAPI is described as 'lets you easily find and connect to practically any API in the world while also providing the easiest way to track and manage the ones you use, in just one place' and is an website in the development category. There are more than 50 alternatives to RapidAPI, not only websites but also apps for a variety of platforms, including Windows, Linux, Mac and Android. The best alternative is Strapi, which is both free and Open Source. Other great sites and apps similar to RapidAPI are Firebase, Supabase, Etebase and GUN.
Nakama is an open-source distributed social and realtime server for games and apps. It has a large set of services for users, storage, and realtime communication; as well as specialized APIs like realtime multiplayer, groups/guilds, and chat.