subZero is described as 'turns your PostgreSQL database directly into a GraphQL & RESTful API' and is an app in the Development category. There are more than 10 alternatives to subZero for a variety of platforms, including Online / Web-based, Mac, Windows, Linux and Self-Hosted solutions. The best alternative is Firebase, which is free. Other great apps like subZero are Etebase (Free, Open Source), Supabase (Free, Open Source), Pubnub (Freemium) and Hasura (Free Personal).
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.
deepstream.io is a clusterable realtime server that handles persistent tcp and websocket connections. It offers data-sync, pub/sub and request/response. It's available for Linux, Mac and Windows and comes with clients in JS, Java and many others.
Backendless is a complete visual app development platform that offers a fully integration UI Builder, real-time database, robust backend with Codeless logic, team-driven development, and bulletproof security.
BackendLab is a web app backend builder which allows you to create and web app backend without writing a single line of code. Define your database models with a simple form and apply field validation, authentication and permissions with a few clicks.