title: Firebase geofencing with custom shapes
body: <p>I am looking to geofence a specific area using Firebase to do things like send alerts to users within a specific area, or perhaps even when they enter an area. I see geosearching capabilities native to Firebase like <a href="https://firebase.google.com/docs/firestore/solutions/geoqueries" rel="nofollow noreferrer">this</a>, but I'm not sure that it gives me a true &quot;geofence&quot; solution. Furthermore, it seems like it only allows me to define areas in the shape of a rectangle, I need to geofence using custom polygons.</p>
  <p>Any advice on how to best utilize Firebase or other systems for this?</p>