"We can't afford downtime" is the sentence that stalls most cloud migrations. It shouldn't. Over dozens of migrations we've refined a playbook that moves legacy workloads to AWS with zero user-facing downtime, and a safe path back if anything looks wrong.
Principle: migrate in reversible steps
Big-bang cutovers are where downtime and disasters come from. We break every migration into small, reversible steps, each independently verifiable. At no point is there a single risky moment you can't undo.
The playbook
- Discover & map dependencies. You can't safely move what you don't understand. We map every service, data store and integration first.
- Establish a landing zone. Accounts, networking, security baselines and IaC (Terraform) so the target is reproducible, not hand-built.
- Replicate data continuously. Stand up the new database and sync it live so it's always current, the cutover moves traffic, not data.
- Run in parallel. The new environment runs alongside the old, validated with real (shadow) traffic before it serves anyone.
- Shift traffic gradually. DNS/weighted routing moves users in small percentages, watching health metrics at each step.
- Keep rollback one switch away until you're fully confident.
A good migration is boring. If the cutover was dramatic, something was designed wrong upstream.
The migration is also a modernization
The biggest mistake is "lift and shift and stop." Moving to the cloud is the moment to add CI/CD, autoscaling, observability and infrastructure-as-code, so the platform is cheaper and more resilient than what it replaced, not just relocated.
Let's plan yours
Tanco Tech runs zero-downtime migrations and managed cloud on AWS and Azure. See our cloud services or book a migration assessment.
