In order to support different configurations for each application instance running on a machine, the NODE_APP_INSTANCE environment variable is inspected, and used for loading instance specific files.

For example, if the NODE_APP_INSTANCE=3 environment variable is set, immediately following the load of default.json, a file by the name of default-3.json will be loaded if present.

This works for all configuration files, so if your NODE_APP_INSTANCE=3 and NODE_ENV=stage, then immediately after loading stage.yaml, a file by the name of stage-3.yaml will be loaded if present.