webtrees is a complex and demanding application. There are a few things you can do to reduce the CPU and memory requirements.
“Is dead” calculations
To protect the data of living individuals, webtrees must calculate whether every individual is living or dead. This process can be slow, as we may need to check dates of children, spouses, grandchildren, grandparents, etc.
You can eliminate these calculations by ensuring that every dead individual has a Death event.
In GEDCOM format, all you need is
1 DEAT Y.
There is a “Data fix” option in the control panel which will add
1 DEAT Y to many (but not all) individuals
whose death can be inferred from dates of close relatives.
Public media objects
A media object will be private if it is linked to one or more private individuals. It is common to have an image linked to many individuals, such as a coat-of-arms or a photograph of a church.
To calculate the privacy of these media objects, webtrees must calculate the privacy status linked record.
If you know that these images will always be public , then you can add an explicit privacy restriction to that record: “Privacy: show to visitors”.
webtrees can use two different PHP extensions to create thumbnail images - GD and ImageMagick. ImageMagick is much faster than GD, so you should install it if you can. See the FAQ entry for thumbnails
Watermarks discourage visitors from downloading public images on your site, and hot-linking to them.
Adding watermarks to thumbnail images is resource intensive. If you do not need watermarks, you can disable this feature in the preferences for each tree.