Hi @razvan_iacob,
If you're running Nginx on a separate server than the rest, you can easily upgrade only the kaltura-nginx and kaltura-ffmpeg packages on that one node, without upgrading the others.
Do not upgrade ffmpeg on the front or batch machines without upgrading kaltura-base to latest because newer versions of ffmpeg may not work with older versions of the server code but upgrading ONLY the Nginx node is safe enough. kaltura-nginx can be used in stand alone mode without having a full Kaltura Server cluster as well.