The Invisible Charset That Silently Breaks MySQL Replication

When Xoom was nearing the completion of a major database migration, replication suddenly stopped, with no warning, no gradual degradation, just a hard halt. The rollback safety net was gone, and the engineering team had no clear path forward.

What followed were weeks of investigation, chasing plausible theories that all turned out to be dead ends. The actual cause turned out to be a silent behavioral change buried deep in a software update, one that quietly altered how the system handled text encoding, in a way that newer and older database versions couldn’t agree on.

In this presentation, Parisa Jamasbi shares the full story: the pressure of a live migration, the frustration of fixes that didn’t fix anything, and the methodical thinking that finally cracked the case.