Amazon ElastiCache for Redis now allows you to modify authentication tokens by setting and rotating new tokens. Redis authentication tokens enable Redis to require a token (password) before allowing clients to execute commands. You can now modify active tokens while in use, or add brand-new tokens to existing encryption-in-transit enabled clusters that were previously setup without authentication tokens. ElastiCache for Redis provides a two-step process that allows you to set and rotate the token without interrupting client requests. 

from Recent Announcements https://aws.amazon.com/about-aws/whats-new/2019/10/amazon-elasticache-announces-support-for-modifying-redis-authentication-tokens/