We will build an application that will demonstrate a few new technologies that can work well with Meteor. Initially, Meteor was a pretty opinionated framework, which is a good thing for many cases where we can speed up the development by removing the need of gluing or reinventing our own stack from scratch. As for the frontend views, we have a good option of using Angular 1-2, React, and Blaze; for a database, that is not the case. Considering that the whole reactiveness comes from the data on the wire, MongoDB paired with Minimongo is the only option that comes with Meteor. There is an experimental package that can integrate Meteor with SQL databases (PostgreSQL in particular), which doesn't seem to get a lot of traction in the community.
Instead of writing a whole bunch of libraries to support all kinds of databases, a better approach will be to have a unified query language...