By default, Matomo runs thousands of regular expressions for each tracking
request to detect what Browser, Device, Operating system, ... is being used and
to detect if a user agent is a bot or not.

This plugin changes this by first looking if a cached result exists for the
particular user agent and if so, directly loads the result from the file
system.

We recommend this plugin only if you have a high traffic website. Depending on
your server it may safe you a few ms per tracking request (say 5ms which may be
say 10% of the total tracking request time).

If you have not that much traffic, the overhead might not be worth it.

Note: We are caching here the user agents that are commonly used on our
website. Depending on your target group the used user agents may differ and you
may benefit less from this cache.

Note: There is no write permission needed for the caching directory as the
cached user agents are already shipped with the plugin and there are no cache
entries created on demand during a tracking request.