serverless-iiif is deployed as a Lambda Function URL, in the lambda-url.AWS_REGION.on.aws domain (e.g., https://fu90293j0pj902j902c32j902.lambda-url.us-east-1.on.aws/iiif/2/). In order to use a custom domain name, or other features like caching and pre/post-processing functions, you'll have to set up a CloudFront distribution (opens in a new tab).