Node.js update db object on save event in another

What is the most convenient way to create/update object on saving changes to other? Imagine we have a model Client and we emit event on save.

clientSchema.post('save', function (client) {
    process.emit('clientUpdate', client);
});

Then we can subscribe for that event like:

process.on('clientUpdate', function(client) {
  //LOGIC GOES HERE
});

Let's assume we want now to update ClientProjection. Where you would locate the listener and how you would implement update logic for mongoDB(mongoose)- using model, by dao, etc.?

via kadiii