How would you build real time geospatial service?

I'm currently using Firebase + geofire to do very basic real time geospatial querying. Due to limitations, I cannot do additional filters, etc. I'd like to take it a step further but don't know much about putting together something real time and geospatial.

The use case is simple, basically people can add animal sighting posts and other people can then comment on them or mark that they also saw such an animal (like bears or coyote). Just for fun, I want to have it be real time so I can see what's in my area and also if the # of coyote seems to be going up, etc. Since its a mobile app, a bunch of mobile clients will be listening for updates on posts in their area.

What database technology can I use to put this together?