I am designing an app that has many topics and for every topic there are some online users and for the same I am using express/socket.io/mongoose as backend and flutter as front end.

I am stuck at a part where I can show users that how many user is currently online for a topic in realtime(shown as list view in the frontend).

Topics are stored in the database.

So for I came up with this bit of logic but I think this is not the right way of doing it.

const roomChangeStream = roomModel.watch();

roomChangeStream.on('change', async (change) => { 
topicModel.find().then((topics) => {
topics.forEach(topic => {
  roomModel.find().where('isSearching').equals(true)
     .where('preferredTopic').equals(topic.slug).count( (err,count)=>{
    if (err) console.error(err);
     console.log("the count for" +topic.slug+" is ",count)
     // socket.emit
  }) 
});
  }).catch((err)=>console.log(err))
})

In the above code, I am looking for change in the room database (where online users are stored) and whenever there is a change I am looping through all the topics (100+) then search for online users count and emit them.

I know this is a bad piece of code. So I am looking for any help