This repo provides a number of Ruby gems (such as pg) to Lambda functions that include this layer, so that they can use those gems without having to bundle them.

Add gems that you want to include in the layer to the Gemfile, then run ./build.sh. You can deploy the layer to AWS by via sls deploy. The output of that command will show the ARN of the layer, which you can then use in the configuration for Lambda functions that use this layer, as described in the Serverless documentation.

This layer can also be deployed via the AWS CLI:

$ cd layer
$ zip -r layer.zip ./lib ./ruby/ -x ./ruby/2.5.0/cache/\*
$ aws lambda publish-layer-version \
         --layer-name gemPacks \
         --region us-east-1 \
         --compatible-runtimes ruby2.5 \
         --zip-file fileb://layer.zip

Based on https://github.com/BranLiang/aws-ruby-lambda-layer, which was based on https://github.com/dschep/sqlite-lambda-layer/