A company replaced an S3-hosted static site at example.com with a dynamic application behind an ALB and added a weighted Route 53 record for the ALB. Some users still see the old static site. How can the engineer ensure only the dynamic content is served for example.com?

The correct solution is to remove the weighted DNS record pointing to the S3 bucket. Even with a weighted record, if the S3 record still exists, some DNS resolvers might occasionally direct traffic to it, especially if the weight isn't zero. Removing the record entirely ensures that no DNS queries can resolve to the old S3 site. Waiting for DNS propagation is crucial because DNS changes take time to update across the internet. Deleting S3 objects might remove the content but doesn't prevent DNS from resolving to the empty bucket, potentially causing errors. Updating the S3 record's weight to 0 is insufficient; some resolvers might still cache the old record or occasionally query it. There's no "domain reset option" for immediate propagation. Configuring S3 to redirect is a partial solution; it relies on users hitting the S3 bucket first, which is what we want to avoid.