Zero-Downtime Kubernetes Migration: Strategies for Live Production Systems

### Planning the Shift Without Taking the System Offline Moving a high-throughput enterprise infrastructure to Kubernetes is not merely a technical overhaul; it is a live surgical operation. Here is the field-tested playbook we use at Sbu Tech to guarantee zero downtime. #### The Phased Migration Pattern 1. **Shadow Traffic Validation:** Duplicate production ingress requests to the new Kubernetes cluster using Envoy or service mesh mirrors. 2. **Dual Database Writes:** Write updates to both legacy and new databases with asynchronous reconciliation workers. 3. **DNS Canary Shifts:** Transition 1%, then 5%, then 25%, and finally 100% of live traffic via Route53 weighted records. 4. **Instant Rollback Gates:** Keep the old infrastructure warm for 72 hours following cutover before commencing teardown.