How to not use Firebase Topics Messaging and Device Group Messaging? - firebase

Question

Wanted to ask in my special case about sending FCM. I read about the Firebase Topic messaging and Device group messaging but dont think it will work in my scenario.
I have a Firebase connected app that need help!
I want to create a place where the app user can send a chat message and there is nobody listening, or there could be a million+ people listening.
There are millions or even billions of chat rooms and there is no way to tell how many are listening on any chat, there could be miljons billions listening, there could be this many notifications to inform users that a new message is posted
When a user sends the chat a message, the notification must be sent to everyone who is listening.
how could I do this?

Answer 1

You can simply use Firebase database to create a chat app as you seek. There are tons of tutorials for that specific application actually.
Typically, the structure would look something like this:
{
"chats": {
"one": {
"title": "Historical Tech Pioneers",
"lastMessage": "ghopper: Relay malfunction found. Cause: moth.",
"timestamp": 1459361875666
},
"two": { ... },
"three": { ... }
},
"members": {
"one": {
"ghopper": true,
"alovelace": true,
"eclarke": true
},
"two": { ... },
"three": { ... }
},
"messages": {
"one": {
"m1": {
"name": "eclarke",
"message": "The relay seems to be malfunctioning.",
"timestamp": 1459361875337
},
"m2": { ... },
"m3": { ... }
},
"two": { ... },
"three": { ... }
}
}
(source)
So whenever a user sends a message through your app, you'd just create a new node under messages and update the appropriate entry under chats. I'd post more about the client-side process, but I'm not sure which platform you're using
EDIT
To clarify a bit further, you should listen to the chats node on your platform for any changes, once the timestamp of the last message changes from what you have stored on device, you check messages. That, or you can simply listen for childAdded in messages.
Regarding your comment, you don't really need FCM in this case unless you want to push notifications, in which case you'll need your own server for that to listen for the changes as well and dispatch the notifications appropriately.