AWS Codebuild workers and image variables

[strowk]

Documentation here suggests to use WORKERS array:

The WORKERS array is filled with filler (or dummy) items to provision the desired number of CI machine instances within the build-matrix strategy and will provide 5 workers to each group defined in the CY_GROUP_SPEC.

I could not find any mention of this in AWS Codebuild documentation.

The same with this part

env:
        variables:
          IMAGE: public.ecr.aws/cypress-io/cypress/browsers:node12.14.1-chrome85-ff81

How is IMAGE variable then used? I don't think that AWS Coudebuild is using it, at least I did not find any mention of that in their docs..