The HTTP 503 can occur when a web hotel has used all of the memory it has available or when a script hours out.
You can see the amount of used memory from the "Website" menu and under "Resource consumption" in the control panel, where you can also read more about how you can lower and analyze the consumption by optimize your page with cache, and find out the problem by examining the log files, and to check for attacks.
We often see that high resource consumption can be caused by attacks, too much traffic or by heavy plugins installed in various CMS systems, especially backup plugins can be problematic.
Ultimately, you can also upgrade your product to a larger one, with more memory, and therefore raising the ceiling, which is also done through our Control Panel.
¶Tips & Tricks
If you want to kill all PHP processes on your website and release all resources, it can be done with the Linux command pkill lsphp through SSH, you can see all active processes with the command ps axf and top d1 .