Chat Feature Tips

Hello!

I am about to build a chat feature into our project with Laravel, NodeJS / ExpressJS and Socket.io and I have a few questions.

First and maybe the most important one:

• How do you save conversation history? Is it inside a database or maybe a file which has file name and file path reference inside a database table?
• Do I have to setup Authentication on the ExpressJS end or Laravel Authentication is all I need to allow logged in users to send messages? Also, is this thing only required only when the NodeJS /ExpressJS part is on a different server and has different routes than the Laravel App?
• The chat will also need to have a "Send File(s)" option. Do I do this with some socket.io package or implement it with something like Dropzone.js using AJAX and deal with the files on the Laravel end?

Any tips are appreciated! Thanks for reading!