How Google migrated billions of lines of code from Perforce to Piper

Google successfully migrated billions of lines of code from Perforce to Piper, a process that took over four years. The decision to move away from Perforce was driven by the need to scale and reduce operational risks. The migration involved creating a new distributed system called Piper, based on Google's infrastructure, and cutting over all traffic to the new system. The project faced challenges such as dependencies on Perforce APIs and the need for a seamless migration process. Despite the risks involved, the migration was completed without any loss of state or impact on Google's production instances. The successful cutover to Piper not only reduced operational risk but also unblocked new systems due to increased traffic support. The migration to Piper showcased Google's engineering daring and scrappiness in tackling complex challenges.