How is application data maintained in containers?

Storing data into "data folders" within the container's writable layer will result in data loss when the container is destroyed.

Storing data in "separate folders" without defining them as volumes does not guarantee persistence beyond the container's lifecycle.

Sidecar containers are used for co-located helper processes, such as logging agents or proxies, not directly for persistent application data storage.

Containers are designed to be ephemeral and stateless, meaning any data written directly inside a container's writable layer is lost when the container is removed or restarted. To maintain application data persistently, containers use volumes, which are separate storage units mounted into the container filesystem and persist beyond the container's lifecycle.