Is there a way to use GeoFire with Firestore?
Edit (Dec 17th, 2020): we have recently released a set of geo utility libraries and a guide to explain how to use them to implement simple geo queries on Firestore!
https://firebase.google.com/docs/firestore/solutions/geoqueries
While we still don't have native geo queries in the database, these Android, iOS, and Web libraries will help you use Geohashes to get geo querying functionality.
Edit (July 1st, 2019): When I originally wrote the answer below I was optimistic that native geo queries would come to Cloud Firestore soon, which clearly did not happen. It's still in the long-term plans, but for now the best option is to use a community-built library or make your own using either GeoHashes or the S2 Geometry library.
The GeoFire libraries for Realtime Database were built using GeoHashes and porting the logic of those libraries to Cloud Firestore should be relatively simple.
Sam from the Cloud Firestore team here. As SUPERCILEX said, Cloud Firestore has support for the GeoPoint data type already. We are working hard to bring native geo queries to the product.
Because native geo queries are coming, we will not be porting GeoFire to Cloud Firestore. Instead we will redirect that engineering effort to getting the native queries sooner.
If you need geo queries today and don't want to build your own library, stick with Realtime Database!
A solution that comes to mind is to add on the Realtime Database just for geo-queries and synchronize the two databases with Cloud Functions, much like Google suggests with presence.
In my case it's not even necessary to synchronize much; I just keep a list of uids with their locations on the Realtime Database and do all geo-queries there.
GREAT NEWS. There is now a library for both iOS and Android that replicates GeoFire for Firestore. The library is called GeoFirestore. It has full documentation and is well tested. I currently use it in my app and it works brilliantly. The code is very similar to that of GeoFire so it should only take a few minutes to learn.