dial tcp:5433 timeout on the auth proxy end when trying connect local private IP address of the AlloyDB instance i/o timeout
failed to connect to instance: Dial error: failed to dial (instance URI = "projects/myproject/locations/us-central1/clusters/mycluster/instances/myprimary"): dial tcp 10.205.117.5:5433: i/o timeout
From the comments:
The problem is accessing from local won't work. AlloyDB currently doesn't implement a Public IP connection, so the only way to connect to it is from within the same VPC (cloud network) as the AlloyDB cluster itself. That's why connecting from a GCE instance on the same network works while connecting from the local machine does not.