Advise with Good Design Patterns When Connecting To An External Database?

I have a regular app using sqlite. I am using a singleton to have a connection to it and perform CRUD operations from it.

I do want to use this with an external database where I would download txt files. I have a database using mongolab and I do know that they have a tutorial to connect directly to the database but I am wondering if this is the right option for me.

What is a good design pattern to connect and keep a connection with an external database such as mongo.

Would it be better to connect to my hosting site and build an API and make calls from android to my API?