Hi,

I am in the process of building a mobile application and releasing it to the AppStore. Currently, we're in a TestFlight Beta with ~ 1500 users with a front-end only native iOS app. Before releasing it to production, we would like to add the following functionalities:

1. User email authentication

2. Being able to store and synchronise individual user's data ( generated while interacting with the app each day -> "user session" ) between various devices

3. Having user session data ( anonymized ) available for an admin via a visual interface for querying, generating insights

4. Simple crud interface for remote configs

5. a/b testing

6. GDPR requirements ( e.g. workflows for removing or exporting user data, ideally a way to keep the anonymized data too )

7. Integration with 3rd party services like Mailchimp or Mixpanel ( which we already use, data is sent directly from the app )

Would appreciate any help with finding the right solution for this case given:

1. Costs (we don't expect large media files storage)

2. Flexibility to add new features related to the backend in the future

3. Infra setup and maintenance

What I've been thinking so far was one of: 1. BaaS AWS/Firebase 2. Custom backend with PostgreSQL 3. PaaS of a Realm type (mobile app already uses Realm for local persistence)

Thanks!