The Context
I recently helped a startup migrate its monolithic Node.js backend to a full AWS serverless architecture. The monolith was deployed on EC2, expensive, and didn't scale well.
The Strategy: Strangler Fig Pattern
Rather than a big bang, we opted for the Strangler Fig Pattern — migrating service by service, keeping the monolith as a fallback.
Phase 1: Identify Bounded Contexts
- Map business domains
- Identify inter-service dependencies
- Prioritize by business impact
Phase 2: Create API Gateway as Facade
- Set up API Gateway in front of the monolith
- Progressive routing to new Lambda services
- Zero downtime via weighted routing
Phase 3: Migrate Service by Service
- Start with the most decoupled services
- Each migration = complete E2E tests before switching
- Feature flags for instant rollback
The Results
- -45% infrastructure costs
- Deploy time from 20min to 2min
- Automatic scalability without intervention
- Improved resilience through service isolation
Pitfalls to Avoid
- Don't neglect cold starts: test with realistic scenarios
- Concurrency limits: plan your reserved concurrency
- Vendor lock-in: abstract AWS services behind interfaces
- Monitoring: invest in observability from day 1
Considering a serverless migration? Let's talk.