Migrating and decomposing APIs with zero-downtime using CloudFront

This article explains how to migrate APIs with zero downtime using CloudFront Functions and KeyValueStore to implement the Strangler Fig pattern for gradual traffic shifting.

• Use CloudFront Functions with KeyValueStore for intelligent, user-aware traffic routing
• Implement three-phase migration: initial state, shadow mode, gradual strangulation, complete migration
• Hash-based user routing ensures consistent routing decisions across requests
• Real-time traffic percentage control enables gradual ramp-up from 0% to 100% without redeployment
• Built-in rollback capability allows instant traffic reversal if issues arise
• AWS CDK sample application provided for deployment and testing
• Consider doubled resource costs during migration and authorization header security implications

This approach enables organizations to modernize APIs while maintaining business continuity through patient, controlled transitions from legacy to new systems.