Cloud Migration Best Practices: A Step-by-Step Playbook for Zero-Downtime Moves

When companies plan a large-scale cloud migration, two goals dominate: zero downtime and meaningful cost control. In this playbook, we share a vendor-agnostic, field-tested approach to migrating workloads to AWS, Azure, or GCP with confidence. You can apply this cloud migration checklist whether you are modernizing monoliths, containerizing services for Kubernetes, or establishing a hybrid architecture. Throughout this guide, we’ll weave in long-tail keywords like “cloud migration checklist for zero downtime,” “Kubernetes migration best practices,” and “Terraform infrastructure as code for multi-cloud” to help you find exactly what you need.

1) Perform a deep discovery and readiness assessment

Start with an honest inventory. Document applications, dependencies, SLAs, data gravity, networking requirements, and compliance constraints. Tag systems by business criticality. Identify quick wins for rehosting and deeper candidates for replatforming or refactoring. Capture baseline metrics for latency, throughput, error rates, and cost—these become your migration success SLOs.

2) Design a target architecture that anticipates growth

Match workloads to managed services where it reduces toil and risk: managed Postgres, object storage, serverless functions, and managed Kubernetes (EKS/AKS/GKE). Use a hub-and-spoke network with least-privilege segmentation. Define HA and DR policies up front. Write your architecture decisions in ADRs so they’re discoverable and reversible.

3) Stand up foundations with Infrastructure as Code (IaC)

Use Terraform or Pulumi to codify accounts, VPCs/VNets, subnets, gateways, DNS, secrets, and observability. Commit everything to version control. Enable policy-as-code to prevent misconfigurations. Automated guardrails—like mandatory encryption and least-privilege—pay for themselves during scale.

4) Establish golden pipelines and automated testing

Create a paved road for builds and deployments using CI/CD. Add smoke tests, contract tests, and performance tests that run per change. Bake in canary and blue/green strategies so cutovers are routine. Your pipeline should be capable of promoting the exact artifact from staging to production.

5) Choose the right migration strategy per system

Not every app needs refactoring. A balanced portfolio might include:

• Rehost (lift-and-shift) for low-risk, time-sensitive systems
• Replatform to containers or managed runtimes to reduce ops load
• Refactor to microservices where clear agility gains exist

Tie the strategy to business outcomes. If the KPI is lead time, favor replatforming first; if resilience is the KPI, invest in refactoring hotspots.

6) Migrate data with change data capture (CDC)

For zero-downtime cutovers, replicate data changes in near real-time using CDC tools (DMS, Debezium, Datastream). Validate row counts and checksums. Run shadow reads against the target DB to validate query plans and indexes. Maintain dual-writes temporarily if required and remove them once the target is authoritative.

7) Plan the cutover like a flight checklist

Freeze non-critical changes. Communicate windows to stakeholders. Canary the first traffic, escalate to 10–30–100% as dashboards validate SLOs. Keep a single-command rollback plan that restores traffic within minutes.

8) Harden security and compliance from day one

Enable centralized identity, enforce MFA, and federate SSO. Segment networks, encrypt in transit and at rest, and rotate secrets automatically. Run continuous compliance scans (CIS, NIST). Document data flows for GDPR/CCPA. Security baked-in beats security bolted-on.

9) Optimize cost with FinOps guardrails

Tag everything. Right-size instances, turn on autoscaling, and use savings instruments like RIs/Savings Plans/Committed Use. Build dashboards that link unit economics (e.g., cost per transaction) to business outcomes.

10) Operate with SRE discipline

Define SLOs with clear error budgets. Instrument golden signals—latency, traffic, errors, saturation. Run regular game days to rehearse failure. Capture learnings in post-incident reviews. Over time, you’ll move from reactive to proactive operations.

Cloud migrations succeed when they’re boring: predictable, observable, and reversible. With this cloud migration checklist for zero downtime and a staged approach to cutovers, you’ll de-risk the journey and accelerate value.