My six side projects are running on a $15 dedicated MongoDB instance provided by DigitalOcean, and I have not faced any issues.

It's super easy and provides the best user experience to connect.

Signup here and get $200 credit → https://digitalocean.com

  1. Create a Create Database Cluster with $15(this will be more than sufficent to grow your side projects.)

When your database is ready, this is how it will look.

Cluster

You can add your source server IP address from which this database can be accessed. You can easily create users and databases. Obtain the connection string and place it into the .env.development file, and your backend will be connected to the database.

That's all.