Dropbox Datastore API Alternatives

Here is the results of my own experiments.

Firebase:

• excellent for realtime events, Web-minded at its core
• multiple auth providers
• local cache in beta for iOS since Dec. 2013, in beta for Android since Feb. 2015
• alternatively, you can use FeventTypeChildAdded and FeventTypeChildChanged to pick the state since last run, but FeventTypeChildRemoved will not be fired to allow deleting data that was removed in the cloud since the previous run of the app. Incidentally, FeventTypeChildChanged does not say which keys have changed
• security is flexible, but needs to be setup for each app and could easily lead to leaked data if not set properly
• the dashboard is great

Cognito:

• probably the closest offering to the former Datastore API, even has the notion of a "dataset", but
• cumbersome to setup
• quite thin currently
• dataset limited to 1MB and entire store to 20MB, which is small
• multiple auth providers
• how will it evolve in the future?

Parse:

• I have yet to experiment, but my current impression from the doc is that the Parse local datastore is not quite like the Datastore cache, i.e. data is either in the cloud or in the local store, but not in both simultaneously. Again, as said, since I have not experimented yet, I could be wrong

CloudKit:

• fully paid by the user like Dropbox, but iOS only and the schema becomes fixed once one enters production (unfortunately)