Years ago I was working on a large Drupal site hosted on AWS with RDS MySQL and ElastiCache for caching. We noticed that ElastiCache was slower than we expected and switched the caching backend over to use the MySQL implementation in a simple KV table, and it was quite a bit faster than ElastiCache for most operations.
People really underestimate how good modern RDBMS are, especially when they have their query cache tuned properly, there's no reason to be slower than Memcache or Redis.
People really underestimate how good modern RDBMS are, especially when they have their query cache tuned properly, there's no reason to be slower than Memcache or Redis.