9 min readJohnny UnarJohnny Unar

Zero-Downtime Deployments: A Practical Guide

Your users shouldn't know you deployed. Here's how to ship code to production without a single dropped request.

Maintenance windows are dead

Maintenance windows are a relic of the past. Your users are global, your competition ships daily, and 'we'll deploy at 3 AM on Sunday' doesn't scale. Zero-downtime deployment means pushing new code to production while the old version continues serving traffic — no errors, no dropped connections, no 'we'll be right back' pages. It sounds like magic, but it's engineering.

Blue-green deployments

Blue-green deployment is the simplest approach. You maintain two identical environments: Blue (current production) and Green (new version). Deploy to Green, run smoke tests, then switch the load balancer from Blue to Green. If something breaks, switch back in seconds. The downside: you need double the infrastructure. For cloud-native apps on platforms like Vercel, Netlify, or AWS with containers, this is handled automatically — every deployment creates a new environment and traffic shifts atomically.

Canary releases

Canary deployments add a layer of safety. Instead of switching all traffic at once, you route 5% to the new version and monitor error rates, latency, and business metrics. If everything looks good, gradually increase to 25%, 50%, 100%. If the canary shows problems, roll back before most users are affected. Kubernetes makes this straightforward with tools like Argo Rollouts or Flagger. For serverless platforms, feature flags (LaunchDarkly, Unleash) achieve the same progressive rollout at the application level.

The database challenge

The hardest part of zero-downtime deployments isn't the infrastructure — it's the database. Schema migrations that lock tables, column renames that break queries, and data transformations that take minutes can all cause downtime. The solution: expand-and-contract migrations. Add the new column, backfill data, update the application to use both old and new columns, then drop the old column in a separate deployment. Never make a breaking schema change in a single step. At steezr, every production deployment is zero-downtime by default. Our clients sleep well on deploy days — and so do we.

Johnny Unar

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Johnny Unar

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Your users shouldn't know you deployed. Here's how to ship code to production without a single dropped request.