Running out of range on a primary key in SQL Server is a ticking time bomb, especially for high-traffic production tables. This article dives deep into the process of migrating a primary key column from INT to BIGINT, tackling challenges like constraints, clustered indexes, and data synchronization. Learn the tested strategies, performance tweaks, and lessons from a real-world scenario involving 650 million rows—ensuring scalability and reliability for your database. Perfect for engineers navigating similar database dilemmas.