asciiresort

I am building a text editor web app.

What is the most suitable cloud storage service for this?

S3 comes to mind.

I am considering having a SQLite DB for each user's set of documents. Not sure SQLite should be used in this way. Is there a storage service for SQLite DBs?

The SQLite website mentions it is the mostly deployed SQL database and found in:

"Every Android device Every iPhone and iOS device Every Mac Every Windows10 machine Every Firefox, Chrome, and Safari web browser Every instance of Skype Every instance of iTunes Every Dropbox client Every TurboTax and QuickBooks PHP and Python Most television sets and set-top cable boxes Most automotive multimedia systems Countless millions of other applications"