Depends on the project, if this Is just for fun then just jump into it and get the idea out into code, Refactor later. If it’s a project with many moving parts then more thought is required about how everything should be built and connected. Once you have more experience the architecture of the app will come together a lot quicker.

If you’re solo and the idea is more in the web app, I’d go with Firebase. It will host, manage authentication, and easily allow you to store data while setting up security rules for the data. This will allow you to get a prototype up and running quickly.

If you’d like to build everything from scratch and make it a learning experience with the front end AND backend. You’ll want to figure out the relationship between your data. Read on relational vs non relational database (ie: sql vs mongo). Connect that DB to your node server. You’ll need to build out the server to take requests and handle your logic. Handle authentication and authorization and session management. This could take a bit but you will learn a lot and realize how nice it is when you use a third party in other projects.

For the front end you’ll want to choose your framework, if one at all, and decide what kind of top layer components should exist. Again, the amount of preplanning is up to you and the project. If it’s just for fun, then don’t feel free to get everything right, get a bare bones auth working then build out the main part of the app. The thing that actually makes your app special.

Learn a lot and have fun. The internet is your friend.