Cloud migration has moved from a strategic option to a business necessity. Organisations that continue to run on ageing on-premises infrastructure face increasing costs, security risks, and operational constraints that their cloud-native competitors simply do not have.
But migration done poorly causes significant disruption — downtime, data loss risk, cost overruns, and frustrated teams. Done well, it transforms how a business operates. This guide gives you the complete framework, from initial assessment through to a stable post-migration environment.
What cloud migration actually means
Cloud migration is the process of moving your business data, applications, and IT infrastructure from on-premises servers (or older cloud environments) to a modern cloud platform — typically AWS, Microsoft Azure, or Google Cloud.
This is not simply copying files to a different location. It involves assessing your current environment, deciding what moves and what gets rebuilt, planning the migration sequence, executing the move with minimal disruption, and then optimising the new environment for performance and cost.
Phase 1 — Discovery and assessment
No migration should begin without a thorough assessment of the current environment. This phase answers four questions:
What do you have? A complete inventory of your applications, databases, servers, storage, and network infrastructure. Many organisations discover systems during this phase that nobody is actively managing — shadow IT that has accumulated over years.
What does each component do? Understand the purpose and business criticality of every system. A payroll application that runs monthly is very different from a customer-facing ordering system that must be available around the clock.
What are the dependencies? This is the most critical and most frequently underestimated part of assessment. Applications rarely exist in isolation. System A writes to Database B which feeds Application C which triggers emails from Platform D. Map every dependency before you plan your migration sequence, because moving one component without understanding its dependencies can break things that appear completely unrelated.
What are the compliance and data requirements? Certain data types — particularly personal data, health records, and financial information — have regulatory requirements about where they can be stored and how they must be protected. Establish these constraints before selecting your cloud environment and architecture.
Phase 2 — Migration strategy
For each application and system in your inventory, you will choose one of several migration approaches. These are commonly referred to as the six Rs:
Rehost (Lift and Shift). Move the application to cloud infrastructure without changing it. Fastest approach, lowest initial cost, but does not take advantage of cloud-native capabilities. Good for systems that work well and simply need to be off ageing hardware.
Replatform. Make limited optimisations during migration — for example, moving a database to a managed cloud database service — without changing the core application. Captures some cloud benefits without a full rebuild.
Refactor / Re-architect. Rebuild the application to take full advantage of cloud-native features — serverless computing, auto-scaling, managed services. Highest effort and cost, but produces the best long-term outcomes for critical applications.
Repurchase. Replace the application entirely with a SaaS alternative. Often the right choice for standard business functions like CRM, HR, or finance systems where cloud-native SaaS products are mature.
Retain. Keep the system on-premises for now. Some applications have dependencies that make migration impractical in the short term. There is no obligation to move everything at once.
Retire. Decommission the system. Every migration reveals applications that are no longer actively used. Retiring them reduces your ongoing cost and complexity.
A typical migration uses all six approaches across different systems. The assessment phase informs which approach is right for each.
Phase 3 — Planning the migration
Once you know what you have and what approach applies to each system, plan the migration sequence carefully.
Start with the lowest-risk systems. Non-critical, low-dependency applications are ideal first migrations. They build team confidence, surface unexpected issues in a low-stakes environment, and produce early wins.
Group dependent systems. Systems that are tightly coupled should migrate together, or in a carefully coordinated sequence with a clear rollback plan if something goes wrong.
Plan for rollback at every stage. Before migrating any system, define precisely what you will do if the migration fails and you need to revert. Test the rollback procedure before you need it.
Set a migration window. For business-critical systems, migrations should happen during low-traffic periods — typically evenings or weekends. Communicate planned downtime to all affected users in advance.
Establish success criteria before migration. Define specifically what "successful migration" means for each system — which tests it must pass, which performance benchmarks it must meet — before you start. This prevents the ambiguity of trying to decide in real time whether a partially migrated system is acceptable.
Phase 4 — Execution
With assessment and planning done, execution is the most controlled part of the process. A well-planned migration rarely surprises. A poorly planned one almost always does.
Execute in the sequence you planned. Document every action taken. Maintain a live log of what has been completed, what is in progress, and what is outstanding. This becomes invaluable if you need to diagnose an issue or hand off to another team member mid-migration.
At each stage: complete the migration, verify against your success criteria, confirm rollback is not required, and then proceed to the next system. Do not proceed past a failed check without a deliberate decision to do so and documentation of why.
Phase 5 — Validation and optimisation
Once systems are running in the cloud, the migration is not complete. A period of parallel running — where the old environment remains available while you confirm the new one is stable — is strongly recommended for critical systems. The duration depends on the application, but two to four weeks is typical.
During this period: monitor performance continuously, compare cloud environment behaviour against the documented baseline from your on-premises environment, address any issues that emerge, and train your team on the new environment.
Once you are confident in stability, decommission the old environment. This is also the moment to begin optimisation — right-sizing cloud resources to match actual usage (over-provisioning is extremely common in initial cloud migrations), setting up auto-scaling where appropriate, and reviewing costs against the business case.
Common migration mistakes and how to avoid them
Underestimating the assessment phase. Organisations that rush to migration without thorough assessment consistently encounter dependency issues that cause cascading failures. Invest the time upfront.
Migrating everything at once. A big-bang migration of your entire environment simultaneously is high-risk and difficult to manage. A phased approach with clear checkpoints is almost always preferable.
Ignoring security configuration. Cloud environments are secure when configured correctly. Misconfiguration is the leading cause of cloud security incidents. Security architecture should be designed before migration, not added afterwards.
Not training the team. Cloud environments are operated differently from on-premises infrastructure. Invest in training your IT team on the new environment before and during migration, not after go-live.
Forgetting about cost management. Cloud costs are dynamic and can escalate quickly without governance. Implement cost monitoring, budget alerts, and resource tagging from day one.
Is your business ready to migrate?
Cloud migration is not right for every business at every stage. If your current infrastructure is working reliably, your team lacks cloud experience, and you do not have the capacity to manage a migration properly, the risk may outweigh the near-term benefit.
The best migrations are planned six to twelve months in advance, resourced properly, and executed in phases. If you are considering migration and want an honest assessment of your readiness and a clear plan for doing it right, that is exactly what our IT assessment covers.
