Willie Yao recently posted a very interesting blog: "How We Partitioned Airbnb’s Main Database in Two Weeks". He describes how Airbnb's engineering team leveraged MySQL Replication to save significant time in their effort to scale their databases:
"Heading into the 2015 summer travel season, the infrastructure team at Airbnb was hard at work scaling our databases to handle the expected record summer traffic. One particularly impactful project aimed to partition certain tables by application function onto their own database, which typically would require a significant engineering investment in the form of application layer changes, data migration, and robust testing to guarantee data consistency with minimal downtime. In an attempt to save weeks of engineering time, one of our brilliant engineers proposed the intriguing idea of leveraging MySQL replication to do the hard part of guaranteeing data consistency."...read the blog!