In about half of the deployments I see "connection timed out" upon invoking redigo api. Surprisingly, it works fine other half of the time without any change to the source or app.yaml.
I also noticed its consistent in a deployment - ie it either connects or not for every request until redeployed.
Given the nature it almost feels like a networking issue. I'm using us-central for vpc connector and ip range 10.8.0.0/28