Overview
This section documents structured approaches for migrating workloads
from on-premises infrastructure to AWS. It outlines migration strategies,
execution phases, architectural considerations, and cost optimization
opportunities during and after migration.
Migration Strategies (6 R's)
1. Rehost (Lift & Shift)
Move applications to AWS without significant changes. Suitable for
quick migrations where modernization is not immediately required.
2. Replatform
Make minimal optimizations such as moving from self-managed database
to Amazon RDS without altering core application architecture.
3. Refactor / Re-architect
Redesign applications to use cloud-native services such as
Lambda, managed databases, or container orchestration.
4. Repurchase
Replace existing applications with SaaS alternatives.
5. Retire
Decommission unused or redundant applications.
6. Retain
Keep certain workloads on-premises due to compliance or latency constraints.
Typical Migration Phases
- Assessment & Discovery – Inventory workloads, dependencies, and infrastructure usage.
- Application Dependency Mapping – Identify interconnections between services.
- Landing Zone Preparation – Setup AWS accounts, VPC, IAM, security guardrails.
- Database Migration – Use AWS DMS or native replication tools.
- Application Migration – Deploy compute resources (EC2, containers).
- Validation & Testing – Functional and performance testing.
- Cutover & Optimization – Switch production traffic and optimize cost.
Architecture Considerations
- Design for Multi-AZ high availability
- Private subnets for databases
- Auto Scaling for application tier
- Secure network segmentation
- Centralized logging and monitoring
Security Considerations
- IAM least-privilege policies
- Encryption at rest and in transit
- Security Groups and NACL layering
- Audit logging via CloudTrail
- Backup and disaster recovery planning
Cost Considerations During Migration
- Temporary dual-running cost (on-prem + AWS)
- Data transfer charges
- Right-sizing post-migration
- Savings Plans or Reserved Instances after stabilization
Post-Migration Optimization
- Enable Auto Scaling policies
- Monitor CPU & memory utilization
- Implement tagging for cost allocation
- Evaluate serverless or containerization opportunities
Key Lessons
- Do not migrate without dependency mapping
- Build landing zone before workload migration
- Optimize only after performance baseline is established
- Plan for rollback during cutover