Simon Willison’s Weblog

Upgrading GitHub.com to MySQL 8.0 (via) I love a good zero-downtime upgrade story, and this is a fine example of the genre. GitHub spent a year upgrading MySQL from 5.7 to 8 across 1200+ hosts, covering 300+ TB that was serving 5.5 million queries per second. The key technique was extremely carefully managed replication, plus tricks like leaving enough 5.7 replicas available to handle a rollback should one be needed.