In Cloud Datastore it's possible to get up to 1,000 entities with an array of keys.

datastore.get( [...keys] )

Is something similar on the roadmap in Firestore? I think this could solve many of the relational challenges like the one referenced above.

user can be member of many teams

Don't think subcollection query would satisfied this case

Instead I think you need

//team doc
{
    "members" : {
         "userID1" : true,
         "userID2" : true,
         "userID3" : true,
         "userID4" : true,
    }
}

var teamQuery = db.Collection("teams").WhereEqualTo("members.{userID}",true);

@Thaina, this is the solution I am currently using. However, this approach is not very scalable. A team couød potentially have thousands of members.

i think same FR already exist
#572

@sondresorbye0111 Then you need the opposite, storing teamID in user doc. Given that the more possible side of relation would be the main to store the less one

And if you need true scalable of both side. Maybe you need another collection, a relationship collection. Which is storing very small document, only

docid : "teamID:userID"
{
    "team" : "{teamID}",
    "user" : "{userID}",
}

And so you could query both way

@Thaina, this is a solution, but it requires two roundtrips to the database. Therefore, I think it would actually be slower than downloading some extra other users IDs.

Thanks for your interest! This is a duplicate of #572.

As we said there, this is definitely on the road map. Right now we're working on stabilizing what we have for GA so this isn't imminent, but this is very high on our list of priorities, don't worry :-).