This document discusses the blue-green deployment strategy, which was created in 2005 to address issues with frequent errors when moving code changes from testing to production environments. The strategy involves running two identical environments, with one environment receiving new code updates while the other continues running the existing code. A load balancer is used to switch traffic between the environments, allowing instant rollbacks if issues arise during testing of the new code version. Benefits include seamless customer experiences, instant rollbacks, and avoiding maintenance windows, while challenges include increased infrastructure costs and ensuring compatibility between code versions.