What is a sidecar container?

Answer

A sidecar is a secondary container that runs alongside the main application container in the same pod to extend or support it without changing the application itself. Common uses include log shipping, metrics collection, configuration syncing, and acting as a service-mesh proxy. Because containers in a pod share the network and can share storage, the sidecar can transparently intercept traffic or read and write the same files. The sidecar pattern keeps cross-cutting concerns separate from business logic and reusable across services.