Cloud migration is not a single event. It is a sequence of decisions about what to move, in what order, with what evidence that it still works. Teams that treat it as a lift-and-shift race usually find the problems after cutover.

Phase 1 — Assessment and inventory

  • List every server, application, database, scheduled job and integration.
  • Map dependencies between systems, including the informal ones nobody documented.
  • Record data volumes, growth rates and retention requirements.
  • Identify compliance, residency and latency constraints.
  • Agree what “done” means for each workload.

Phase 2 — Target architecture

Decide what gets rehosted, replatformed, rebuilt or retired. Rehosting is faster but preserves old constraints; rebuilding costs more but removes them. Most migrations should be a mix.

Phase 3 — Migration waves

Group workloads by risk and dependency. Move a low-risk workload first to prove the process, then increase complexity. Each wave needs a rollback plan and an owner.

If you cannot describe how to move a workload back, you are not ready to move it forward.

Phase 4 — Data and cutover

  • Rehearse the data transfer and measure how long it actually takes.
  • Define a freeze window and who can approve an exception.
  • Validate row counts, checksums and business totals, not just “the site loads”.
  • Prepare DNS changes, certificates and firewall rules in advance.
  • Run a communication plan for staff and customers.

Phase 5 — Post-move verification

Test the journeys that matter: login, search, checkout, payment, email, reports and integrations. Monitor errors, latency and background jobs for at least a full business cycle before declaring success.

Phase 6 — Decommission

Retire the old environment deliberately: remove DNS records, archive data, cancel licences and confirm nothing still points at it. Leaving old servers running is a common source of quiet cost and security risk.

Common mistakes

  1. No dependency map, so a forgotten integration breaks on cutover day.
  2. Testing only the homepage instead of complete business transactions.
  3. No rollback because everyone assumed it would work.
  4. Migrating everything at once to save time.
  5. Forgetting email, DNS and certificate expiry.

If you need help planning a move, our cloud migration service and managed hosting team can assess your estate and build a phased plan.