What is Blue-Green Deployment? — UK Software Development Guide
Direct Answer
Blue-green deployment is a release strategy that reduces downtime by running two identical production environments — "blue" (current live) and "green" (new version). When the new version is ready, traffic is switched from blue to green instantly. If problems are detected, traffic can be switched back to blue immediately. Blue-green deployments enable zero-downtime releases and instant rollback.
Blue-green-deployment in the UK
Blue-green deployment supports UK FCA operational resilience requirements. PS21/3 requires regulated firms to demonstrate the ability to remain within impact tolerances during disruption — including during software updates. Blue-green deployment provides: zero-downtime releases (no service interruption for users), instant rollback (critical for FinTech where a broken release can affect payment processing), and the ability to run smoke tests against the new version before switching traffic. NHS suppliers should consider blue-green for clinical systems where any downtime during clinical hours requires incident reporting.
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