I inherited a WordPress server with multiple websites on a MySQL 5.6 database sized at over 500MB. Most of the space was in around 200,000+ spam comments no one had been monitoring or removing. I used some plugins to automatically clear much of the junk, then manually deleted what wasn’t caught by the tools. Unfortunately, without a tool to optimize the databases they remained bulked up. WP-Optimize had good reviews, I imported the SQL from the cleaned-up VM, and have run WP-Optimize a bit more, and we’re under 60MB for the entire database size. Works beautifully!