It sounds like you need to look at a server-side solution. AWS (S3) may be part of that solution - but not the full solution. There are lots of solutions for server-side applications - and the one that you choose will depend on which platform and programming you want to work with. E.g. you can use a JavaEE solution, NodeJS, PHP, Ruby on Rails, Python (e.g. Django), etc...
Once you have the server-side infrastructure set up to handle user accounts and events and event registration, you can create a web service interface to it which your CN1 app will interact with.
Steve