Migrating Legacy Microservices to Modern Java and TypeScript

"Modernize the legacy stack" is a phrase that strikes dread into every senior engineer's heart — and for good reason. Migration projects fail at a notoriously high rate. They balloon in scope, break running systems, and produce tech debt that rivals what they replaced. I led successful migrations of critical microservices to modern runtimes, containerized deployments, and event-driven architectures — on time, without downtime, and with measurable gains in performance and reliability. This article distills the frameworks, patterns, and hard lessons from those engagements into a practical guide for teams facing similar challenges.