What is Zero Downtime Deployment?

Zero Downtime Deployment (ZDD) is a deployment strategy that ensures the application remains available throughout the entire rollout process. By using techniques like rolling updates, blue-green deployments, or canary releases, new versions can be rolled out without users experiencing interruptions or errors.

Why am I getting 502 Bad Gateway during deployment?

This typically happens because Kubernetes terminates pods before the load balancer has removed them from the traffic flow. The solution is to implement a preStop hook that adds a delay (typically 15-30 seconds), and ensure the application handles SIGTERM correctly with graceful shutdown.

What is the difference between Liveness and Readiness Probe?

Liveness Probe checks if the process is running and should be simple (don't check database here). If it fails, Kubernetes restarts the pod. Readiness Probe checks if the pod is ready to receive traffic (database connection ok, cache warm). If it fails, the pod is removed from traffic flow without restart.

How do I migrate a database without downtime?

Use the Expand-Contract pattern: 1) Add new columns/tables without removing old ones, 2) Update code to write to both and read from new, 3) Migrate existing data, 4) Remove old columns when all pods are running new code. This ensures backward compatibility throughout the process.

What is GitOps and why should I use it?

GitOps is a practice where Git is the "single source of truth" for infrastructure and application configuration. Tools like ArgoCD automatically synchronize the cluster state with what is defined in Git. This provides full traceability, easy rollback, and eliminates the need for the CI system to have direct access to production.

How much does it cost to implement Zero Downtime Deployment?

Costs vary based on existing infrastructure and complexity. A typical implementation requires investment in Kubernetes cluster, CI/CD tools (GitLab/GitHub), and ArgoCD. The biggest investment is often upskilling and refactoring the application to follow 12-factor principles. ROI comes quickly through reduced downtime and increased developer velocity.

Case Studies

Zero Downtime.
Full Control.

Zero Downtime Deployment

11 min readOctober 1, 2025

Deployments

99.99% uptime

api-gateway v2.4.1production

2m ago

web-frontend v3.1.0production

14m ago

worker-service v1.8.3staging

28m ago

auth-service v4.0.2production

1h ago

12Pods

<30sRollback

-85%Deploy

Rollback1

Scale pods2

Canary deploy

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Full Control.