Your Deployments Keep Failing Because You Re Not Using Readiness Probes Here S What S Actually Happening

Your deployments keep failing because you're not using readiness probes. Here's what's actually happening.

Kubernetes doesn't know when your app is actually ready to serve traffic. It only knows when the container started.

Those two things aren't the same.

Your app might need to load config, warm up a cache, establish database connections, or run migrations. That takes time. But without a readiness probe, Kubernetes assumes the pod is good to go the moment the container is running.

What goes wrong without readiness probes:

Kubernetes starts your new pod. The old pod gets terminated. Traffic routes to the new pod immediately, but your app is still initializing. Requests fail, users see errors, and your deployment "succeeded" but your app is down.

Readiness probes fix this.

A readiness probe tells Kubernetes "don't send traffic to this pod until it responds healthy on this endpoint." Kubernetes keeps checking. Once the probe passes, the pod gets added to the service. Until then, traffic keeps going to the old pods.

No dropped requests. No mystery errors during deploys. No rollbacks because something "worked" but didn't.

The fix is simple.

Add a readiness probe that hits a health endpoint your app exposes. Something like /healthz or /ready that returns 200 when the app is actually ready to handle requests. Set an initialDelaySeconds that gives your app time to start up.

If you're deploying to Kubernetes without readiness probes, you're one slow startup away from a bad deploy.

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