Document every service the current platform provides
List workloads, ingress routes, storage classes, secrets, policies, operators, admission controls, certificates and external dependencies. Record resource use and disruption constraints from telemetry rather than requested values alone.
Rancher may also provide cluster lifecycle, access and policy functions that applications do not reveal. Decide which capabilities EKS, AWS services or separate tools will replace.
- Workload owners and business criticality
- Persistent volumes and data movement
- Identity, RBAC and service accounts
- Ingress, DNS and certificate flow
- Logging, metrics, alerts and audit records
- Backup and restore procedures
Build and validate the EKS foundation
Prove network reachability, IAM integration, node lifecycle, autoscaling, storage, image access and observability before application teams arrive. Apply policy and security controls through code so the same environment can be recreated.
Document the support boundary between the application team, platform owner and AWS account owner. This prevents a production incident becoming an ownership debate.
Sequence workload waves
Choose a representative non-critical service for the first end-to-end move. Include its deployment, secrets, network route, monitoring and rollback. The first production wave should be small enough to reverse within the agreed window.
| Phase | Validation |
|---|---|
| Foundation | Access, networking, storage and observability |
| Pilot | Build, deploy, traffic and rollback |
| Production waves | SLOs, data integrity and incident response |
| Retirement | No traffic, scheduled task or data dependency remains |
Experience from a production migration
Saikat led work moving on-premise Rancher Kubernetes workloads to AWS EKS, alongside a large Jenkins migration. The supplied experience record reports a 40% reduction in environment provisioning time after the broader platform change.
This example comes from Saikat's employment history and is presented as individual delivery experience. A new engagement needs its own baseline and cannot assume the same result.
Risk note: Do not decommission the source cluster based on successful smoke tests alone. Confirm traffic, scheduled workloads, backups, audit requirements and rollback expiry.
Prove platform services before application teams arrive
A new EKS cluster is not ready when its nodes join successfully. Application teams depend on DNS, ingress, certificate issuance, image access, identity, secret retrieval, policy, logging, metrics, alerting and sometimes storage or service-mesh behaviour. Each required capability needs an owner, configuration source, upgrade path and acceptance test.
Identity deserves early testing because AWS, Kubernetes and CI/CD boundaries meet during deployment. Prove how engineers, workloads and pipelines authenticate; which namespaces and AWS resources they can reach; how access is reviewed; and what happens when a credential or role changes. Avoid reproducing broad legacy permissions simply to make the pilot pass.
Observability should work before performance or failure testing. Logs, metrics, events and user-visible signals must be available to both the platform owner and the application team. Otherwise a migration wave can pass a basic smoke test while hiding degraded dependencies or restart behaviour.
- Ingress, DNS, certificates and external load-balancer behaviour
- Workload and pipeline identity with least-privilege AWS access
- Secret source, rotation and namespace boundaries
- Image registry, admission policy and deployment provenance
- Logs, metrics, alerts, events and cost visibility
Write the cutover and rollback runbook around observable states
The runbook should state the source and target versions, data or state assumptions, traffic change, validation owner, stop conditions and rollback trigger. Use observable checks such as successful business transactions, error rate, queue behaviour and dependency health. “The pods are running” is not a sufficient production acceptance test.
Lower DNS time-to-live only when it supports the chosen traffic plan, and account for clients or intermediaries that cache longer. For stateful services, define whether writes can occur in both environments, how data consistency is checked and which system remains authoritative. A rollback that loses accepted writes is not a safe rollback.
After traffic moves, keep enhanced monitoring for a defined window and restrict unrelated platform changes. Record the outcome and update the next wave rather than treating every workload as identical. The source environment is retired only after dependencies, recovery obligations and retention requirements are closed.
Risk note: Rollback must be technically and operationally possible. A runbook with no tested identity, data or traffic reversal is only a statement of intent.
Frequently asked questions
Can Rancher and EKS run in parallel during migration?
Yes. Parallel operation supports staged cutover, but teams must control configuration drift and define which platform is authoritative for each workload.
How should workloads be grouped?
Group them by business risk, dependency and data movement. Namespaces alone rarely represent migration complexity.
What proves the migration is complete?
Production telemetry, workload-owner acceptance, tested recovery and confirmation that no traffic, scheduled jobs or data dependencies remain on the source platform.
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