TL;DR This is Phase 4 of the FSx for ONTAP S3 Access Points serverless patterns collection. Building on the Phase 1 foundation , the 14 industry patterns from Phase 2 , and the near-real-time + ML + observability stack from Phase 3 , Phase 4 delivers: DynamoDB Task Token Store : Correlation ID pattern solving the 256-char SageMaker tag limit for production Step Functions Callback workflows Real-time Inference + A/B Testing : SageMaker Multi-Variant Endpoints with intelligent routing and automated comparison metrics Multi-Account Deployment Patterns : StackSets templates, cross-account IAM roles with S3 Access Point policies, and CloudWatch Cross-Account Observability for enterprise-scale rollout Event-Driven Architecture Prototype : Standard S3 bucket events → EventBridge → Step Functions achieving 3.5-second E2E latency , as a future-compatible prototype for native FSx ONTAP S3 AP notifications All features are opt-in via CloudFormation Conditions (default disabled, zero additional cost).…