So what do most of your current customers do for data storage? I mean, I doubt they all use CosmosDB? (simply because it's not particularly mainstream)
We use existing technologies. Anyone can use any cloud Database service. We've datacenters on San Fransisco and in Belgium. So, based on those users can choose where they need to deploy their DBs.
Usually we recommend to configure databases via env variables. Users can also use our [now secrets](https://zeit.co/docs/getting-started/secrets) service as well to avoid hard-coding secrets.
Spanned databases are great, but most of the time performance is not there (It's getting there, but it needs to be there for a year before people start to care)