What is the best backend service for a mobile application for a startup?

Question

Startups

At the first stage, a database is required, a reaction to events, the ability to send push notifications, the ability to easily implement a correspondence component for multiple users. As well as the ability to easily take all your data from the service for subsequent migration.

Answer 1

Given the wide range of tasks, the service will not work . Firebase will solve the issue with the database and authorization, Realm and CloudKit with synchronization. Firewall pushes can be done through CloudFunc, but it's a pain.
Given the messenger, you need WS - but the service does not have them (Firebase and Realm have a simulation through pushes).
Need your back , offhand from the next. technologies: authorization by taste, silent pushes for updates, pushes for the event project, WS for the messenger, database (the type depends on the project).
The answer is only in the context of your question, it is not a universal schema.