@aws-amplify/cli-internal/templates/amplify-skeleton/backend/backend-config.json

Amplify CLI

{
  "api": {
    "amplifyDatasource": {
      "service": "AppSync",
      "providerPlugin": "awscloudformation",
      "output": {
        "authConfig": {
          "additionalAuthenticationProviders": [],
          "defaultAuthentication": {
            "authenticationType": "API_KEY",
            "apiKeyConfig": {
              "description": "",
              "apiKeyExpirationDays": 7
            }
          }
        }
      }
    }
  }
}