in source/backend/lib/cdk-photosearch-web-stack.ts [31:35]
private getAssetSourceBucketName(): string {
// %%BUCKET_NAME%% part is replaced by build-s3-dist.sh.
// regional assets are stored in the "bucketprefix-{region}"
return `%%BUCKET_NAME%%-${cdk.Aws.REGION}`;
}