Service Deployment 101 - Part 1

A release/deployment of a service happens when its source code has changed or when its configuration has changed. So, I would see a release as a function of service source code and configuration

Service Release = f(Service Source Code, Service Configuration)

Also, here, Configuration = Secrets (API keys, passwords etc) + Non-secretive configuration (DB hostname etc). So it's best to treat all configuration as secrets and keep it safe and secure