Pods created after the first try to load the private files using the same path as the first one I'm currently working on deploying Drupal8 on Openshift to achieve horizontal scaling, but I hit a problem.

On a single pod (ie: "server" running drupal"), everything seems to be ok so far. But when I'm deploying a new pod, it tries to load the private files (/sites/default/files) using the same path as the first pod.

I guess it's because something is cached in the DB since "Clearing all cache" fixes it.

Is there something in the configs I can do to prevent this behaviour ? And do you think of something I should be warned about when trying to achieve horizontal scaling ?
Posting my comment as an answer.

sites/default/files needs to be on a shared file system so that Drupal can work correctly. This contains uploaded and generated files (e.g. CSS/JS).

If you do this, you probably want to move twig to a local temporary folder, see Can I change the location of the cached Twig templates?. Note that you then need to take care of emptying that folder on all servers when you do a deployment (Unless you do something really special, this cache only needs to be updated when you change your template files).