MongoDB configuration at Platform.sh

How the replica set works at Platform.sh?

How to do a query on a MongoDB database using a UI client such as MongoDB Compass?

To connect to MongoDB, or any other service, from your local system, first open an SSH tunnel using the platform tunnel:open command. That will establish a secure connection to your environment from your local computer and expose local ports you can connect to.

You can then enter the credentials into your local tool, be it MongoDB Compass or otherwise. The host will be localhost, the port will be one of the 30xxx ports reported by tunnel:open, and the user and password can be obtained by running platform relationships.

See the documentation for more details.