Definition
Blue-green deployment is a software release strategy that minimizes downtime and risk by running two identical production environments, called Blue and Green. During a deployment, the new version of the application is deployed to the inactive environment (e.g., Green), while the current version runs on the active environment (e.g., Blue). Once the new version is tested and verified in the Green environment, traffic is switched from Blue to Green. This allows for instant rollback if issues arise, as the Blue environment remains untouched and ready to take over. This method is crucial for maintaining high availability and ensuring a seamless user experience, especially in critical applications. A common confusion is mistaking it for canary releases, which gradually roll out changes to a subset of users. Blue-green deployment offers a complete switchover, making it ideal for applications requiring zero downtime.