Are you trying to have a separate database per user / account? Then you are in a though spot
Ive tried that with Meteor, but doing it dynamically and in just one process is difficult. An alternative would be to go for 1 docker container per customer to run meteor in and that container would have its own dedicated connection.
Meteor does this, because it tracks changes in Mongo and pushes them from the database connection up untill the client in realtime. Simply switching connection would stop that tracking for a previously connected user.
Another solution would be to create a collection per user, but this requires you to create your own low level publications and some nasty logics to initialize collections when users log in and out. I would not recommend this approach.
A third option is to avoid meteor’s serverside minimongo and go for your own mongo connection. This allows you to simply connect, query, push and disconnect from the database on demand. (You can still use pub sub fpr this though and it allows you to use the clientside connections)
Then again, is having a separate db per user really needed? Can’t you simply use query filters to fetch user specific data? This allows you to easily create some microservices and separate your databases based on domain instead of customer