Blue/Green WebLogic Active Environment Controller implements a zero-downtime deployment pattern across two isolated EC2 node clusters in a multi-AZ VPC, with a Lambda-based router dynamically switching traffic via Parameter Store configuration. External consumers and cross-account services (Accounts B, C, D) route through an ALB to the Lambda router, which reads the active-env parameter and directs requests to either the Blue or Green WebLogic cluster. This architecture eliminates deployment downtime and enables instant rollback by toggling a single configuration value, critical for mission-critical Java workloads requiring SLA compliance. Fork this diagram on Diagrams.so to customize subnets, instance types, or add cross-account IAM policies for your multi-tenant environment. Consider adding SNS notifications to the Lambda router to alert teams when environment switches occur.