Amazon Redshift now enables users to add and change sort keys of existing Redshift tables without having to re-create the table. The new capability simplifies user experience in maintaining the optimal sort order in Redshift to achieve high performance as their query patterns evolve and do it without interrupting the access to the tables.

from Recent Announcements https://aws.amazon.com/about-aws/whats-new/2019/11/amazon-redshift-supports-changing-table-sort-keys-dynamically/