Designing a New BaaS: Looking for Community Input on APIs, Logic, Realtime, and Data Formats

I’m working through the early design phase of a potential Backend-as-a-Service platform and would like to gather insights from developers who have experience with Supabase or similar systems.

I’m specifically trying to understand expectations in the following areas:

1. API Model How do you prefer to interact with your backend: automatically generated APIs based on schema, fully custom logic, or a hybrid approach that provides both out of the box?
2. Execution Layer When handling business logic, do you prefer serverless functions, logic built directly into the backend framework, or access to both depending on the workload?
3. Realtime Features What do you expect from realtime capabilities? Should updates depend solely on database events, or should the system also support custom event streams, function-driven events, or other models that give more control?
4. Data Format For client communication, would you rather work with JSON, or a more compact binary protocol with automatic serialization and deserialization handled by the SDK and backend? How important is it for the SDK to abstract these details completely?
5. Custom Logic Language If you were writing custom backend logic, which language would you prefer to use? Would you expect support for multiple languages, or is one well-integrated runtime enough?

I’m aiming to build something that matches real development patterns rather than assumptions. Any feedback, preferences, or examples from your own projects would be extremely helpful.

Thanks for taking the time to share your thoughts.