Building a YT Analytics / Post Scheduler

Hi, i am going to try (and hopefully succeed) a Youtube app as a Saas, now, i already know the Stack i will be using (or not, kkkkk),
i am going to use React obviously and probably NextJs , for the backend normal NodeJS, now here it comes the problem, database, i have no idea of what type of database (postgres,mysql...) or service ( aws, azure... ) To use, RIP. Can someone help me? i know this is going to be hard, that's why i am going to make it first as a personal object and later if it works as intented and with no bugs... i would scale it to a Saas and offer it at a price!
Soooooo, can someone help me on choosing the stack in terms of storaging users and their information, + the actual post scheduler (this one i quite know what to do already, my problem would be more of how to handle the upload/save the videos to my database and make the script know which ones to post ( i know on this case i can do " NodeJS calls the database every minute to retrieve all the videos that need to be sent out that minute. " ))
I've seen a user use Fauna as a database for twitter scheduling, and another one (owner of feedhive.io) use AWS Amplify. I don't really know what to do in this part!
So can you help me, kek?!