Cloud migration is not a single decision — it is a programme of decisions: what to migrate, when, to which cloud provider, using which approach, and in what sequence. Getting the strategy right before the first workload moves is the difference between a successful migration and an expensive failure.
Why Businesses Migrate to the Cloud
The primary drivers of cloud migration are infrastructure cost reduction, scalability, reliability, and development velocity. On-premises infrastructure requires capital investment in hardware, facilities, and IT staff. Cloud infrastructure is operating expenditure — pay-as-you-go — with built-in redundancy and global reach. Cloud-native development patterns (containerisation, managed databases, serverless functions, CI/CD pipelines) significantly accelerate software delivery compared to traditional on-premises deployment models.
Secondary drivers include improved disaster recovery (cloud providers offer multi-region replication at a fraction of the cost of equivalent on-premises DR), access to managed AI and analytics services, and end-of-life hardware forcing a migration decision regardless.
The 6-R Migration Framework
Every workload in a migration should be assessed against the 6-R framework to determine the appropriate migration approach:
Rehost (Lift and Shift)
Move VMs or containers to cloud infrastructure without code changes. Fast, low-risk, suitable for workloads that simply need infrastructure modernization. Does not produce cloud-native benefits. Cost: typically 60–70% of the cost of replatforming the same workload.
Replatform (Lift, Tinker, and Shift)
Make targeted cloud optimisations — migrating to a managed database service, containerising the application, or switching from a self-managed queue to a managed queue service — without changing the core application architecture. Balances migration speed with cloud optimisation.
Repurchase
Replace a self-hosted application with a SaaS equivalent. Replace self-hosted email with Microsoft 365; replace on-premises CRM with Salesforce; replace self-managed file storage with SharePoint or Google Drive. Often the right decision for commodity business functions.
Refactor / Re-architect
Redesign the application to be cloud-native — decomposing a monolith into microservices, adopting serverless compute, or redesigning data architecture to use cloud-native databases. Highest cost and complexity; highest long-term benefit. Appropriate for core applications that need to scale significantly or where development velocity is a strategic priority.
Retire
Decommission applications that are no longer used or whose function is covered by another system. Migrations are an opportunity to retire redundant applications and reduce portfolio complexity. Typical programmes retire 10–20% of their application estate during migration.
Retain
Keep certain workloads on-premises — typically because they have regulatory requirements for physical data location, because they are tightly coupled to on-premises hardware (manufacturing control systems, for example), or because migration cost exceeds benefit. Retain should be a deliberate decision, not a default.
The Five Phases of a Cloud Migration
Phase 1: Assess
Inventory the application estate. Document each application's dependencies, data volumes, traffic patterns, and business criticality. Identify compliance requirements. Score each workload against the 6-R framework. Output: a migration portfolio with a prioritised migration sequence and a total cost of migration estimate.
Phase 2: Foundation
Establish the cloud foundation before migrating any workloads: cloud account structure, network topology (VPCs, subnets, connectivity to on-premises), security controls (IAM policies, logging, monitoring), cost management (tagging standards, budget alerts), and the CI/CD pipeline. Skipping the foundation phase produces security gaps and cost overruns.
Phase 3: Pilot Migration
Migrate 1–3 non-critical workloads first. Validate the migration approach, tooling, and runbooks. Identify gaps in the foundation. Build team confidence. Do not migrate business-critical systems until the pilot is complete and validated.
Phase 4: Migration Waves
Migrate workloads in waves, grouped by dependency and criticality. Typically: non-production environments first; then less-critical production workloads; then business-critical systems. Run old and new environments in parallel during transition to allow rollback.
Phase 5: Optimise
After migration, continuously optimise cloud spend and architecture. Right-size compute instances; use reserved instances for stable workloads; implement auto-scaling; adopt managed services to reduce operational overhead. Cloud optimisation typically reduces post-migration costs by 20–40% within the first year.
Choosing a Cloud Provider
AWS is the market leader with the broadest service catalogue. Best for teams that want the widest range of managed services and the largest global infrastructure footprint.
Azure is the best choice for organisations heavily invested in Microsoft technologies (Windows Server, SQL Server, Active Directory, Microsoft 365). Azure's hybrid cloud integration with on-premises Microsoft environments is genuinely superior.
Google Cloud (GCP) is the strongest choice for data and AI workloads, with BigQuery and Vertex AI being industry-leading managed services. Also competitive on Kubernetes (GKE is the most mature managed Kubernetes service).
Most businesses migrating to cloud for the first time should choose a single provider and commit, rather than distributing workloads across multiple clouds from the start. Multi-cloud complexity is a management overhead that rarely justifies itself for businesses below $50M ARR.
Planning a cloud migration?
Brillminds runs cloud migration assessments that produce a prioritised migration portfolio, cost model, and technical roadmap. We execute migrations on AWS, Azure, and GCP. See our cloud services.
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