The migration nobody noticed

The scariest sentence in platform engineering is "we need to migrate the database of a live system." Ours had real-time bidding on it. Money on the line, every minute. We didn't have access to the legacy codebase, its infrastructure, or even its internal database configuration. So we built the new platform in parallel and used Debezium CDC to stream every change from the old system into the new one, continuously, until the two were mirrors. Cutover day was the most boring day of the whole project. That was the point. Bidders never saw a blip. Lesson: the best migrations aren't clever, they're rehearsed. We ran the sync for weeks, measured drift, and cut over only when the diff was zero and stayed zero.