Quick answer
Before migrating business applications to the cloud, inventory applications and dependencies, choose a migration approach for each such as rehost, replatform or refactor, estimate running costs with realistic sizing, plan security, backup and access, define data migration and cutover steps, test performance and confirm who will operate and monitor the environment afterwards.
Key takeaways
- Inventory dependencies before choosing a migration approach.
- Lift-and-shift is fastest but rarely the cheapest to run.
- Estimate ongoing cloud costs, not just migration effort.
- Plan operations, monitoring and security ownership after migration.
Who this guide is for
IT managers and business owners considering moving on-premise servers or hosted applications to AWS, Azure, Google Cloud or similar providers.
Inventory applications and dependencies
List every application, database, file share, scheduled job and integration, with owners and usage. Map dependencies such as which application reads which database or which systems connect over the local network. Hidden dependencies, such as a printer or a licence server, are a common cause of failed migrations.
Choose an approach per application
Rehosting moves servers as they are and is fastest. Replatforming makes moderate changes, such as moving a database to a managed service. Refactoring changes the application to use cloud services more fully, costing more but potentially improving scalability and cost. Some applications are better replaced by software-as-a-service or retired.
Estimate costs realistically
Use the provider’s pricing calculator with realistic sizing based on actual usage, not on oversized on-premise servers. Include compute, storage, databases, backups, data transfer, monitoring, security services and support plans. Compare with total current costs including hardware refresh, power, space and staff time. Reserved or committed-use pricing can lower costs for stable workloads.
Plan security and access
Define identity and access management, network design, encryption, firewall rules and logging before migration. Apply least privilege for administrators. Understand the shared responsibility model: the provider secures the infrastructure, but you secure your configuration, data and access. Enable logging of administrative actions from day one and review it regularly, since misconfiguration is a more common cause of cloud incidents than provider failure. Agree who approves new access and how quickly access is removed when people leave.
Plan data migration and cutover
Decide how data moves, how long it takes, how changes during migration are captured and when users switch. Test the migration with a copy, verify data completeness and plan a rollback. Schedule cutover during low-usage periods and communicate with users. Agree in advance who decides to proceed or roll back on cutover day, and which checks they will use to make that decision.
Test performance and connectivity
Applications that worked on a local network may be slower over the internet, especially if they make many small database calls. Test with realistic users and locations. Branch connectivity, VPNs and bandwidth may need upgrades. Include peak periods such as month-end processing in performance tests, and measure from the locations where staff actually work. If performance is not acceptable, options include moving more components together, caching or changing how users access the application.
Plan operations after migration
Someone must monitor, patch, back up, optimize costs and respond to incidents. Decide whether your team, a managed service provider or a mix will do this. Set budgets and alerts to avoid unexpected bills. A readiness assessment typically covers inventory, approach, costs, security, data migration, testing and operating model.
Scope checklist
- Are all applications and dependencies inventoried?
- Which migration approach suits each application?
- What are realistic monthly running costs?
- Who will operate and monitor the cloud environment?
- Has a rollback plan been tested?
Frequently asked questions
Is cloud cheaper than on-premise servers?
It can be, depending on workloads, sizing, optimization and how operations are handled. Poorly sized or unmanaged cloud environments can cost more than expected.
What are the 6 Rs of cloud migration?
A common framework lists rehost, replatform, refactor, repurchase, retire and retain as options for each application.
How long does a cloud migration take?
Small migrations can take weeks; larger portfolios take months. Duration depends on the number of applications, dependencies, approach and testing.
Prepared with AI assistance as an engineering decision guide. Examples are illustrative unless explicitly labelled as an internal implementation. No independent expert review or customer outcome is claimed.
Concerned about an existing system?
Share what the system does, who maintains it today and what is going wrong. Scope, access, dependencies and commercial terms are agreed before delivery. Do not submit passwords, API keys or confidential records.
