Haven't figured out how to send a request from host, but verifying that is the next step.

Not sure what you exactly mean, but docker-compose exposes the service port to host, so you should be able to simply

yarn run-feature-flags-service-in-sandbox
# in a separate terminal
curl "http://localhost:50055/features?platform=..." # etc

That's exactly what I've done, but I have to figure out why it didn't work.

@jon could you explain a little bit what do you mean by

The canonical way to handle args would be to use case for the positional arguments, then continue to consume the input with shift. But that would be more effort than just assuming we will have 1 or 2 arguments.

Which part of the code does it correspond to?

Haven't figured out how to send a request from host, but verifying that is the next step.

Not sure what you exactly mean, but docker-compose exposes the service port to host, so you should be able to simply

yarn run-feature-flags-service-in-sandbox
# in a separate terminal
curl "http://localhost:50055/features?platform=..." # etc

The issue was caused by a fact that I was using localhost instead of 0.0.0.0. When running the service locally, there's no difference. But when a service is run within a container, the localhost doesn't work properly.