Firebase realtime database structure in chat app

sorry for my bad English level, I'm from Argentina.

I have the following messages data structure in Firebase:

"messages"
   "-KezmqXSdKCNFFA432Uc___-KfCEwklG_y3naRDIUiY"
         "messageDate": "20170620"
         "messageTime": "18:44" 
         "message": "Hi"
   "-KezFDSAADFASFFS3221___-KASDF32324SDFASD1FS"
         "messageDate": "20170620"
         "messageTime": "22:23" 
         "message": "How are you?"

Where -KezmqXSdKCNFFA432Uc, -KfCEwklG_y3naRDIUiY, -KezFDSAADFASFFS3221 and -KASDF32324SDFASD1FS are users.

My problem is that I created a childEventListener in "messages" node to receive new users messages but I am receiving all the new messages of all the users (I'm logged in one user per app) because my childListener is in "messages" node.

Is it correct that if I have 1000 users when adding a message, a new message reaches the 1000 users? (Assuming that within the app, you can check to which user that message belongs).

Thanks!

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.