Application configuration, that differ for separate environments, such as databases, external systems, or credentials, need to be existent at runtime. This configuration should not be reflected in the source code but dynamically modifiable from outside of the application. This implies that configuration is retrieved via files, environment variables or other external concerns.

Container technology and orchestration frameworks support these approaches as previously shown. Configuration for different environments, such as test, staging, and production is stored in Kubernetes config maps and dynamically used in pods in volumes or environment variables.

The 12-factor principles state that an application "[...] stores config in environment variables". Environment variables are a straightforward way of inserting specific variations that is supported by all kinds of technology. However, if configuring the application involves a lot of individual configuration values, engineers may consider to use configuration files contained in container volumes, instead.