This blog post explores how to ensure a Kubernetes sidecar container starts and becomes ready before the main application container. Native sidecar containers in Kubernetes start before the main application, often almost simultaneously, which isn't always desired. The author investigates readiness probes, startup probes, and postStart lifecycle hooks to delay the main application's start until the sidecar is ready. Using a readiness probe alone doesn't delay the main app's start. A startup probe, correctly configured, effectively delays the main application until the sidecar is ready. The post also briefly mentions postStart hooks as an option. Liveness probes primarily restart the sidecar and don't influence the main application's readiness. The key finding is that a startup probe is the most effective method for delaying the main application's start. The author concludes by emphasizing the importance of controlling container startup order when the main app depends on a sidecar. This offers a solution when modifying the application code is not possible.