Migrating an A/B Testing API to Google Cloud: Zero Downtime and a Non-Blocking Cache

Photo by NASA on Unsplash In 2019 I led the migration and performance work for our company-wide A/B testing platform — the system product teams use to run experiments and read assignment in production. This post is a concise case study: why downtime was unacceptable, what we found in pre-migration review, how we fixed blocking cache refreshes with Java and Guava , and how we rolled out to Google…