I recently lead a project where I migrated a customer’s application backend to AWS. Its an e-commerce/marketplace platform with its core backend built with a microservices architecture.
Here are key notes to consider when migrating a similar workload.
1. Infrastructure as Code is Essential
- Use Terraform with modular architecture for consistent deployments
- Separate modules for ECS services, task definitions, and target groups
- Environment-specific configurations (e.g prod.tfvars) for scalability
2. Service Discovery & Communication
- Implemented AWS Service Connect for inter-service communication
- Both HTTP and gRPC endpoints configured for each service
- Service mesh approach eliminates hardcoded service endpoints
3. Load Balancing Strategy
- Single ALB with path-based routing e.g (/admin/* , /order/* , etc.)
- Priority-based listener rules for 7 services
- Cost-effective compared to individual load balancers per service
4. Security & Configuration Management
- AWS Systems Manager Parameter Store for environment variables
- IAM roles with least-privilege access per service
- Secrets management separated from application code
5. Observability & Monitoring
- Centralized logging with CloudWatch Log Groups
- Service-specific log streams for easier debugging
- Health check endpoints for each service
6. Deployment & Scaling Considerations
- Fargate for serverless container management
- Circuit breaker pattern for deployment safety
- Auto-scaling capabilities
7. Network Architecture
- Multi-AZ deployment across 3 availability zones
- Public subnets for ALB, private subnets for services
- Security groups for network-level isolation
8. Service Organization
- Clear service boundaries: admin, notification, order, ship, store, user, wallet
- Consistent naming conventions and tagging strategy
- Modular Terraform structure for maintainability
9. Container Strategy
- ECR for private container registry
- Standardized port configurations (HTTP + gRPC)
- Resource allocation (CPU/memory) per service requirements
10. Operational Excellence
- GitHub Actions for CI/CD automation
- Terraform state management for team collaboration
- Parameter scripts for environment setup automation
These lessons demonstrate a well-architected microservices migration focusing on scalability, security, and operational efficiency.
Fargate vs EC2-Based ECS: Key Migration Lessons
Why Fargate Was Chosen
1. Operational Simplicity
- No EC2 instance management (patching, scaling, monitoring)
- AWS handles underlying infrastructure completely
- Eliminated capacity provider complexity
2. Cost Optimization for Microservices
- Pay-per-task model better for 7 small services
- No idle EC2 capacity costs
- Right-sizing at container level (256 CPU, 512 MB per service)
3. Security Benefits
- No SSH access or EC2 security hardening needed
- Automatic security patches by AWS
- Network isolation at task level with awsvpc mode
4. Simplified Networking
- Each task gets its own ENI
- Direct security group assignment to tasks
- No port mapping conflicts between services
5. Auto-scaling Efficiency
- Task-level scaling vs instance-level
- Faster cold starts for microservices
- No pre-provisioned capacity waste
Trade-offs Accepted
1. Higher Per-vCPU Cost
- Fargate costs ~40% more than EC2 equivalent
- Justified by reduced operational overhead
2. Limited Customization
- No access to underlying OS
- Can't install custom agents or tools
- Fixed networking and storage options
3. Cold Start Considerations
- Slightly longer task startup times
- Mitigated with health check grace periods ( in my case 120s)
Fargate Sweet Spot
For 7 lightweight microservices with variable traffic, Fargate eliminated infrastructure management complexity while providing better resource utilization than maintaining EC2 instances that would often run underutilized.
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