Cloud Migration Strategy for 2025: What to Move, What to Keep, and How to Do It

Cloud Migration in 2025: The Context

By 2025, most greenfield applications are built cloud-native. The cloud migration challenge is primarily about legacy systems — on-premises servers, hosted bare-metal infrastructure, and first-generation cloud deployments that predate containers and managed services. Companies with these systems are increasingly feeling the pain: escalating maintenance costs, inability to scale elastically, security risks from unpatched infrastructure, and inability to attract engineering talent who want to work with modern infrastructure.

The 6R Framework: What to Do With Each System

AWS's 6R framework provides a useful decision tool for each application in your portfolio:

1. Rehost (Lift and Shift): Move the application as-is to cloud VMs. Fastest, least risk, least benefit. Use for: applications you plan to retire within 2 years, or applications with regulatory constraints that prevent modernisation.
2. Replatform (Lift, Tinker, Shift): Move with minor modifications to take advantage of managed services (e.g., replace self-managed MySQL with RDS). Reduces operational burden without full rewrite. Best for: stable applications that would benefit from managed services.
3. Refactor/Re-architect: Redesign the application to be cloud-native — microservices, containers (ECS/EKS), serverless (Lambda). Highest benefit, highest cost and risk. Use for: applications that are core to your business and need to scale significantly.
4. Repurchase: Replace the application with a SaaS product (e.g., move from self-hosted CRM to HubSpot). Best for: commodity applications where SaaS is mature and total cost of ownership favours subscription.
5. Retire: Decommission applications that are no longer needed. Cloud migrations often uncover 20–30% of applications that nobody actually uses — these can be shut down.
6. Retain: Keep on-premises for now. Appropriate for: applications with data sovereignty requirements, recently upgraded on-premises infrastructure with years of life remaining, or regulatory constraints.

AWS vs GCP vs Azure: Which Cloud?

For most India-based businesses and teams building for Indian users:

• AWS: Best default choice. Largest service catalogue (250+ services), most mature India region (ap-south-1 Mumbai, ap-south-2 Hyderabad), deepest talent pool in India, best documentation. Most government compliance frameworks (MeitY, SEBI, RBI cloud guidelines) have AWS as a reference.
• GCP: Best for AI/ML workloads (TPUs, Vertex AI, BigQuery ML). Google's data centre infrastructure (lowest latency for many workloads). Preferred by companies already heavily using Google Workspace.
• Azure: Best for enterprises already on Microsoft stack (Windows Server, SQL Server, Active Directory, Microsoft 365). Seamless hybrid with on-premises Microsoft infrastructure. Strong BFSI (banking/financial services) compliance posture in India.

Data Migration: The Hard Part

Application migration is usually straightforward. Data migration is where cloud projects fail. Key principles:

• Migrate data in parallel, not cutover: Run old and new systems simultaneously. Sync data bidirectionally (using CDC — Change Data Capture — tools like Debezium) until the new system is validated. Then cut over traffic gradually.
• Validate before cutover: Row counts match. Checksums match. Business-critical queries produce the same results in old and new systems. Write automated validation scripts, not manual spot-checks.
• Have a rollback plan: For every migration, document how you'd roll back within 30 minutes if the cutover fails. Never migrate without a tested rollback procedure.

Cloud Migration Cost in India

India-based cloud migration costs:

• Simple lift-and-shift (3–5 servers, basic applications): $8,000–$15,000
• Replatform to managed services (RDS, ECS, ElastiCache): $20,000–$40,000
• Full re-architecture to cloud-native microservices: $60,000–$150,000+
• Large enterprise data centre to cloud (50+ servers, complex integrations): $150,000–$400,000

Cloud infrastructure running costs post-migration typically run 30–40% of equivalent on-premises hardware costs (when on-premises is at end of depreciation). Factor in the elimination of hardware maintenance, data centre space, and infrastructure engineering time.