[bumblebee4]

PouchDB is CouchDB-Protocol implemented in javascript so you can run it wherever there is javascript, not just as a client. If you want to have a backend, you can use any DB that supports that protocol (there are several), which includes using a PouchDB instance run by node.js.

[lhuser123]

Is PouchDB + CouchDB considered an alternative to Firebase?

[bumblebee4]

That depends on your use case since Firebase is more than a database. Since CouchDB is from 2005 and Firebase is from 2011, it is in comparison a very mature product and protocol worth trying.