Flexible Datasync is described as 'Flexible DataSync is a BAAS with a complete client framework. Developers can build real-time applications and communication services and deploy them easily'. There are more than 50 alternatives to Flexible Datasync for a variety of platforms, including Online / Web-based, Windows, Linux, Mac and Android. The best alternative is Firebase, which is free. Other great apps like Flexible Datasync are Meteor (Free, Open Source), GUN (Free, Open Source), remoteStorage (Free, Open Source) and Nakama (Free, Open Source).
An open protocol for per-user storage OWN YOUR DATA Everything in one place – your place. Use a storage account with a provider you trust, or set up your own storage server. Move house whenever you want. It's your data.
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.
Etebase makes it easy to build end-to-end encrypted applications by taking care of the encryption and its related challenges. Think Firebase but encrypted in a way that only your users can access their data.
5apps helps both developers and users to get the most out of the Web as a software platform. 5apps Deploy is a turn-key deployment and hosting platform for client-side web apps. 5apps Storage is a new kind of cloud storage for the Web, based on an open protocol.