Firebase realtime database structure in chat app

Thanks to @Linxy for a brilliant answer

I have created a firebase database regarding @Linxy answer

Here is the complete JSON export

{
  "Chats" : {
    "-Lsfsd234xda" : {
      "lastMessageSent" : "-LrDEBo1-Message",
      "members" : [ "-LrDEBoLokW-5mhaT3ys", "-LrDEBoLokW-5mhaT3yz" ],
      "more_properties" : "goes here"
    }
  },
  "Users" : {
    "-LrDEBoLokW-5mhaT3ys" : {
      "id" : "-LrDEBoLokW-5mhaT3ys",
      "userDisplayName" : "Qadir Hussain",
      "userEmail" : "[email protected]",
      "userPhotoUrl" : "https://lh3.googleusercontent.com/a-/AAuE7XXXXXXXXX"
    },
    "-LrDEBoLokW-5mhaT3yz" : {
      "id" : "-LrDEBoLokW-5mhaT3yz",
      "userDisplayName" : "Ishaq Bhojani",
      "userEmail" : "[email protected]",
      "userPhotoUrl" : "https://lh3.googleusercontent.com/a-/AAuE7mB3KTbXXXXXXXX"
    }
  },
  "chatMessages" : {
    "-Lsfsd234xda" : {
      "-LrDEBo-MessageUID" : {
        "message" : "Hi there!",
        "messageDate" : "10/10/2019",
        "messageTime" : "10:16pm",
        "sentBy" : "-LrDEBoLokW-5mhaT3ys"
      },
      "-LrDEBo1-MessageUID" : {
        "message" : "Hello",
        "messageDate" : "10/10/2019",
        "messageTime" : "10:17pm",
        "sentBy" : "-LrDEBoLokW-5mhaT3yz"
      }
    }
  },
  "userChats" : {
    "-LrDEBoLokW-5mhaT3ys" : {
      "0" : "-Lsfsd234xda",
      "1" : "-Lsfsd234xda1",
      "chatUID" : "-Lsfsd234xda"
    }
  }
}

If you do a structure like similar to this:

-chats
   - chatUID
       - members
           - userUID
       - lastMessageSent:messageUID
       - ... more properties  

-chatMessages
   - chatUID
     - messageUID
         - sentBy: userUID
         - messageDate:""
         - messageTime:""
         - message:""

-userChats
    - userUID
       - chatUID

you can attach a listener to /userChats/userUID, which will display active chats, and a listener to /chatMessages/chatUID, which will get all chat messages for a specific chat conversation.

This way is a lot easier to setup firebase security rules, and users will only receive chat messages which they are apart of.