Creating process.env variables using AWS Amplify?

You can add variables at your Amplify environment configuration. You can also add variable overrides and select a branch that's gonna use it.

DOCS: https://docs.aws.amazon.com/amplify/latest/userguide/environment-variables.html

After a year+ of development using amplify framework I figured that you can only specify ENV VARIABLE form from your front-end build process. for lambdas it's a bit tricky. You can add a condition "IsProductionEnv" which is going to place value to ENV Variables for that function depending on amplify env. for production I use "prod" you can use whatever you want. go to your amplify/backend/function/{functionName} folder. there should be {functionName}-cloudformation-template.json file. you need to add one more item to "Conditions" object:

"Conditions":{
  ...,
  "IsProductionEnv": {
      "Fn::Equals": [
        {
          "Ref": "env"
        },
        "prod"
      ]
    }
}

then you need to use that condition at "Resources.Properties.Environment.Variables" :

       "Environment": {
          "Variables": {
            ...,
            "STRIPE_PK": {
              "Fn::If": [
                "IsProductionEnv",
                "pk_live_...",
                "pk_test_..."
              ]
            }
          }
        }

I have "dev" and "prod" amplify env names. it will handle your deployments and manage your env variables based on env for that function.