The 6 Rs of Cloud Migration: How to Choose the Right Strategy for Each Workload

Why You Need a Strategy Per Workload, Not One Plan

The biggest mistake in cloud migration is treating a portfolio of 200 applications as a single project with a single approach. Some apps should move untouched in a weekend. Some should be rewritten. Some should be switched off entirely. The 6 Rs framework, originally popularized by Gartner and refined by AWS, gives you six named strategies so you can tag every workload and plan realistically. You run the assessment once, then execute in waves.

The Six Strategies

1. Rehost (Lift and Shift)

Move the application as-is to cloud infrastructure, typically VM to EC2, with no code changes. This is the fastest path and the lowest immediate risk. Tools like AWS Application Migration Service replicate servers and cut over with minutes of downtime.

Choose it when: you have a deadline (a data center lease ending), a large volume of similar servers, or a commercial app you cannot modify. Trade-off: you inherit all the inefficiency of the original design and see limited cloud savings until you optimize later.

2. Replatform (Lift and Reshape)

Make a few targeted cloud optimizations without changing the core architecture. The classic example: move a self-managed MySQL database onto Amazon RDS, or containerize an app and run it on ECS instead of raw EC2. You get managed backups, patching, and scaling for a fraction of a full rewrite.

Choose it when: a handful of changes unlocks meaningful operational savings. This is the sweet spot for many workloads: more benefit than rehost, far less effort than refactor.

3. Repurchase (Drop and Shop)

Replace the application with a SaaS product. Migrating a self-hosted CRM to Salesforce, or a legacy email server to Google Workspace, means you stop maintaining it entirely.

Choose it when: a commercial product covers your needs and the app is not a competitive differentiator. Watch for: data migration effort and the licensing cost that replaces your infrastructure cost.

4. Refactor (Re-architect)

Rewrite significant parts of the application to be cloud-native: breaking a monolith into services, adopting serverless functions, or moving to managed event streaming. This delivers the most agility, scalability, and long-term cost efficiency, and it costs the most up front.

Choose it when: the application is business-critical, needs to scale in ways the current architecture cannot support, and will be actively developed for years. Never refactor an app you plan to retire in 18 months.

5. Retain (Revisit)

Keep the workload where it is, for now. Some applications have compliance constraints, recent hardware investments, or dependencies that make migration premature. Retaining is a legitimate decision, not a failure, as long as it is deliberate and revisited.

6. Retire

Turn it off. A portfolio assessment routinely finds that 10-20% of applications are no longer used or are duplicated by another system. Every app you retire is one you do not have to migrate, secure, or pay for. This is the cheapest win in any migration.

How to Choose: A Practical Decision Path

1. Inventory everything. You cannot plan what you cannot see. Build a list of every application with its owner, dependencies, traffic, and business value.
2. Ask if anyone still uses it. If not, tag it Retire.
3. Ask if a SaaS product replaces it. If yes and it is not a differentiator, tag it Repurchase.
4. Ask about the timeline and constraints. Compliance lock-in or a hard deadline pushes you toward Retain or Rehost.
5. Weigh effort against benefit for the rest. Low-effort, decent-benefit workloads go to Replatform. High-value, long-lived, scaling-constrained apps justify Refactor.

A useful rule of thumb for a first migration wave: rehost or replatform the majority to get out of the data center quickly, refactor only the two or three apps where cloud-native architecture drives real business value, and retire aggressively.

Estimating Effort and Cost Per Strategy

Rough relative effort helps set expectations with stakeholders. Retire and Retain cost almost nothing to execute. Rehost is measured in days to a couple of weeks per application group once tooling is in place. Replatform adds a few weeks for the targeted changes and testing. Repurchase effort is dominated by data migration and user retraining rather than engineering. Refactor is the outlier, often months of engineering per application, which is exactly why you reserve it for the handful of workloads that justify it. On the cost side, remember that migration spend and run-rate spend are different budgets: a cheap-to-migrate rehost can be expensive to run if left unoptimized, while an expensive refactor can slash the monthly bill. Model both when you build the business case, and get finance involved early so the cloud bill does not become a surprise.

The Pitfalls That Derail Migrations

Lift and shift then forget. Rehosting without a follow-up optimization plan leaves you paying for oversized instances running 24/7. Budget a right-sizing and reserved-capacity pass within 90 days of cutover. Cloud bills after a naive lift and shift are frequently higher than the old data center.

Underestimating data gravity. Moving terabytes takes time and bandwidth. Test transfer speeds early and consider physical transfer appliances for very large datasets.

Ignoring dependencies. An app that looks standalone often calls three internal services. Map dependencies before you schedule a cutover, or you will migrate one app and break four others.

No landing zone. Migrating into an unstructured account with no networking, identity, or guardrails creates a security and cost mess. Build the foundation (accounts, VPCs, IAM, logging) before the first workload lands.

Getting the assessment and landing zone right is where experienced help pays for itself. A cost-optimized AWS foundation built before migration prevents the runaway bills that follow careless lift-and-shift, and ongoing DevOps as a service gives you the hands to execute waves without pulling your product engineers off the roadmap.

Plan Your Migration With Senior Engineers

InstaDevOps provides senior DevOps engineers on retainer to run your portfolio assessment, build a secure AWS landing zone, and execute migration waves without downtime. Plans start at $2,999/mo (Startup) and $4,999/mo (Business), with engagements typically starting within about 48 hours. Book a free 15-minute call to scope your migration.