How do I handle stateful sessions during migration?

Eliminate stateful sessions by externalizing session state (Redis/Memcached) and using short TTLs. During cutover, reduce stickiness TTL to seconds or disable it. Drain old pods with connection max age and preStop hooks to close sessions gracefully.

What if my database can’t support CDC?

Use native logical replication where possible (Postgres, MySQL). If not, schedule chunked backfills with application-level version markers and strictly idempotent writes. Expect a longer soak period and consider a brief read-only window for truly hard edges (rare).

Can I skip feature flags and just deploy the new version?

You can, but then rollback is slow and blunt. Flags make read/write paths and behaviors independently switchable, which shortens MTTR dramatically. If you hate vendor lock-in, use OpenFeature with your provider of choice.

How do I prove readiness to leadership?

Share rehearsal metrics: peak RPS sustained, p95/99 latencies within budget, automated rollback firing in staging, data parity reports with mismatch rates, and the exact runbook with decision points and owners.

What’s the minimum toolset to pull this off?

Kubernetes or a reliable orchestrator, GitOps (ArgoCD/Flux), traffic shaping (Istio/NGINX), observability (Prometheus/Grafana), and a feature flag system. Everything else is optimization.

Guides · Oct 19, 2025 · 10 minute read

The Zero‑Downtime Migration Checklist We Actually Use in Production

A pragmatic, step-by-step playbook to cut over critical workloads without waking up pager duty or your CFO.

Alex Kim

Principal Architect, GitPlumbers

20 years shipping and fixing distributed systems at scale. Led platform teams at a top-10 retailer and a fintech unicorn. Enjoys deleting YAML, not adding it.

You don’t get points for being brave. You get points for never paging the on-call.

Back to all posts

The Zero‑Downtime Migration Checklist We Actually Use in Production

Key takeaways

Implementation checklist