I am new here.
This is rather a choice-based question rather than purely technical one.
Many mobile apps authenticate with Cognito, and I am going to use the same for ease of use + free tier advantage.
However, to enable some functionality, I must also store some user data on AWS RDS (postgres). I am wondering about my choice though:
I am relatively unaware of all complexities of custom user authentication (I have successfully implemented using Cognito already), and am wondering if I am losing a lot by going for quick and easy Cognito solution?
There will obviously be some duplication of data fields between both Cognito and RDS. User UUID or email. Is this normal? How successful apps usually handle it?
Is backup from Cognito cost-effective? For example, how much it could cost if I have a lambda to back up my 100K users from Cognito?
What is cost effective in the long run? Having everything in Cognito or my own RDS database?
Is migration even possible (from Cognito to my RDS) - as it totally depends upon clients wanting to upgrade the app?
MOST IMPORTANT: In general, how does the data sync between Cognito and RDS happen? Is there a popular approach I am missing out?
If I am supposed to use a pre-built identity provider, I have already made up my choice about using Cognito (since my other stuff is already on AWS) - so I am not keen on considering Auth0 at least at this point - just to narrow down my choice.
