NGINX Reverse Proxy is working well. Using the cache it's possible to store static content on every Reverse Proxy to reduce traffic on the main server. I can set a time after the last access it will be removed - so far I know.
Having more Reverse Proxies - is it possible to sync the cache between the Reverse Proxys or preload a special file to all of them? And if yes, how I can do it? This would be a good speed up for new bigger files.
You could locate the cache files and synch them across your servers with something like rsync.
To pre-load a cache you‘d have to curl each possible URL.