This could be many things, I test the code that powers the plugin against five different versions of the PHP programming language (5.3, 5.4, 5.5, 5.6, 7.0R5) and have not experienced major issues, it could be the sum of many things at once which all together may translate to a noticeable latency.
I will post here what I wrote in other ticket…
There are two things that could be affecting the load time of a page in a WordPress site when the Sucuri plugin is active […];one are the DNS lookups executed on the “init” hook and the other is the event monitor.
The DNS lookups, depending on the configuration of your server, may increase the latency as they depend on the response time of the DNS server used by your hosting provider; normally this only increases by milliseconds but in some cases they may take seconds to execute. This is the same in every programming language, but in PHP the latency is very noticeable.
As for the event monitor, this is the basic feature of the plugin and is the main source of data to populate the audit logs; without them it is pointless to have the plugin installed; but it is worth to say that the problem is not strictly with the plugin’s code but with the network of the server, if for some reason the communication between the server and the Sucuri API service takes more time than normal to be established then the same latency will be noticeable in every event that is being monitored by the plugin.
There is no immediate solution for this because as you can read there are external dependencies that can not be control from the plugin’s code; I can not make PHP work faster nor the DNS lookups as these are things that only your hosting provider can improve.
I will continue investigating this and if I find a real solution I will include it in a new version of the plugin; for the time being if you continue experiencing this slowness I suggest you to keep the plugin deactivated until a new version is released.
