About connecting to a remote MySQL database secure

Hello everyone!
At this day, im planning to my app comuncate with a remote MySQL database. Where I have the info of the customers that have purchased or rented my software.
If the app CANT connect to the server in order to check customer’s payment status. So then app wont able to start.

At this point i’m ok, and I have no doubts about how to do that.
But then it comes to me a single and powerful Question:

What about the SECURITY?

HOW can I do this secure, inorder to prevent a sniffer attack and the data keep secret and keep safe to be exposed to the web

Set SSLMode = True in the MySQL connection.

Or instead of a MySQL connection, have the server expose an API you can call over HTTPS using TLS and then put all the sensitive stuff inside a POST payload and not in query string variables in the URL.