Risks about setting useUnifiedTopology to false

Hi there, im using replica set and multi-region nodes with Atlas.
At the code side i’m using singleton pattern so i use the same connection always. If i set useUnifiedTopology to false, what are the risks?
I’ve read the documentation at Unified Topology Design but it don’t seems clear to me.
Most important thing i want to be sure its if the connection will be alive even if there is any down time in a certain node.

  • I’m not using readPreference option at connection config.
  • Set useUnifiedTopology to true is not an option because NestJs MongooseModule always creates two connections per service and im close to connections limit, needed refactor its to expensive for the reason that we have close to 50 services.