>If you use Varnish Cache on your website or are visiting a website that caches content with Varnish Cache, chances are at some point you will come across the Varnish Cache server error: Error 503 Service Unavailable / Guru Meditation with an XID number. A 503 error means that the web server trying to be reached is unavailable - this could be because it is overloaded, down for maintenence, or not fully functional for another reason. > >When you see this error in relation to Varnish Cache, it means that the website is using Varnish Cache to cache and serve content, and that Varnish Cache is unable to reach the back end server. Varnish Cache issues the Guru Meditation error when a connection has timed out or the Varnish Cache server has made too many requests to the back end server without getting a response. Instead of making an infinite number of requests to an unhealthy back end, Varnish Cache issues the 503 error to let the visitor (and website owner) it is likely the website manager is already working on a fix and your best bet is to try again later. If you are the website manager or owner and aren’t sure why you are getting this response, read below to find out.