## What happened
My .NET Core 3.1 app runs in a Docker container on AWS ECS with Fargate, and I couldnt connect to a new Aurora MySQL cluster via the writer endpoint. Postman calls through the load balancer threw a transient failure exception about enabling EnableRetryOnFailure in the UseMySql call. I tried the retry pattern and it still failed. Another user hit the same thing in 2024.
## The fix that worked
The problem wasnt transient at all, it was the connection string: the Terraform endpoint property included the port number, so the server part read dbcluster:3306 and the .NET MySQL driver choked on it. Changing server=dbcluster:3306 to just server=dbcluster fixed the connection. If youre building the connection string from Terraform outputs for ECS/Fargate, strip the :3306 off the server value.