How to use docker for building a web application

My question comes from try to wrap my head around traditional MySQL<->php<->html/css/js Web app. I am building an app using all latest technologies as a training exercise.

I am narrowed down to the following frameworks

1. MongoDB in backend
2. MemcacheDB & Memcache to store cache data
3. ExpressJS to create APIs
4. Angular 2 on the front end.

Each of these technologies I know how to use in isolation. How can I build it out in a way that my final goal of deploying it to AWS leveraging docker to simplify it.?

1. I read that isolating docker containers are best. What would be my docker containers here?
2. How would ExpressJS connect to mongoDB and store value in AWS?
3. Will stopping my MongoDB docker container destroy its data?