A developer is debugging an AWS Glue job that reads from S3 and writes to Amazon Redshift. Bookmarks are enabled and maximum concurrency is set to 1. The job writes successfully to Redshift, but subsequent runs reprocess files that were already loaded in earlier runs. What is the most likely cause?

The most likely cause is that the AWS Glue job is missing a commit statement after writing to Amazon Redshift. When writing to Redshift from Glue, especially with bookmarks enabled, a COMMIT command is essential to finalize the transaction and make the changes permanent. Without a commit, the data might appear to be written successfully during the job run, but the transaction isn't finalized, and AWS Glue bookmarks won't correctly record the processed state. Consequently, subsequent runs will reprocess the same files because the previous writes were not committed. Incorrect options: s3:GetObjectAcl permission is not directly related to bookmark functionality for Redshift targets. Bookmarks primarily track S3 object processing based on object metadata and the job's internal state. Maximum concurrency set to 1 is a performance setting, not a cause for bookmark failure. It simply means only one instance of the job runs at a time. An older version of AWS Glue is unlikely to be the sole cause of this specific bookmark issue if the job otherwise runs and writes data.