After over a decade of hosting itself in the data center, Etsy.com moved to the Google Cloud Platform (GCP) in 2018. In this talk, I'll go over:why the company decided to make the transitionour architectural approaches to migrating a large monolith, and the difficulties we faced gaining confidence in themthe assumptions we never knew about and had to fix: in the application code, the infrastructure tooling, and our processescutting over to GCP, safelythings we learnt running there for the last 9+ months