The Wiki Replicas are replicas of the production databases. Many tools on Toolforge use them.
Tool developers may use Docker and docker-compose for local development environment (see eg rTHER or R1969). But once the tool attempts to connect to the replicas, the connection fails.
The documentation already suggests to use SSH tunneling for local testing which makes use of Wiki Replica databases
Idea: providing a Docker image that does the proxying, which you can attach to your compose project and get replicas access :)