"Error 503 Backend fetch failed" sometimes

[ntsite]

Hello.

Today I faced this error while reaching my page with Wordpress several times. (XID: 3659737).

After some minutes I tried again, and it worked. What causes this error?

 

[bdistler]

What causes this error?

The error [ Error 503 Backend fetch failed ] - usually indicates that the web server is temporarily under more than normal load - OR your script did not produce a result within about thirty seconds (PHP time-out limit)