For reference, if anyone does expand on this in future IIRC, the following info might be worth being aware of.

It's possible to split these out to separate compose.yaml files and use the Docker Compose feature include or the merge/override feature to share common configs.

Notably, you will have trouble merging YAML lists/sequences, which I think is only supported by multiple -f overrides (requires the same service name), whereas for YAML maps you can use Fragments / Extensions (YAML anchors/aliases + YAML merge << syntax).

• That can make environment more suited to map style instead of list, since that supports both forms.
• One notable difference over volumes with configs is that a bind mount volume will persist changes to disk whereas the configs approach here is useful for immutable init state when creating the container, but it can be modified after at runtime.
  • Re-creating the container will start with the initial config in compose.yaml again. This is the main value besides self-containing the example into a single file.
  • It might be possible to get the same with volumes if some of the volume driver has a setting to emulate one-way sync (:ro / read-only does but it prevents writes in the container)..

If there are separate YAML snippets to be composed, you just run docker compose config instead of the equivalent docker compose up to output the full compose.yaml. If examples grow it may be useful to know about that :)