Burst to Region: Overflow AWS Outposts workloads to Amazon EC2

This article describes the Burst to Region pattern, which automatically overflows AWS Outposts workloads to Amazon EC2 in the parent Region when local capacity is exhausted, maintaining availability during peak demand.

• Detects capacity constraints on Outposts using CloudWatch alarms on InstanceTypeCapacityUtilization metrics
• Launches overflow EC2 instances in the parent Region via Lambda-orchestrated Auto Scaling groups
• Gradually shifts traffic using Application Load Balancer weighted target groups to minimize latency impact
• Implements stepped weight progression (90/10, 70/30, 50/50) rather than abrupt transitions
• Recovers by scaling down overflow fleet when Outposts capacity drops below threshold
• Requires stateless workloads or external session stores (ElastiCache, DynamoDB) for state management
• Uses EventBridge scheduled rules every 5 minutes for safe recovery evaluation and gradual scale-down
• Best suited for internal applications, stateless web frontends, and pre-processing tiers tolerating single-digit millisecond latency increases

The pattern trades moderate latency increases for continued availability during capacity events, with complete deployable AWS SAM templates available in the GitHub repository.