Plugin slowing down big website with many images

No, this behaviour can not be changed without modifying the code of the plugin and you are the very first one to report this. If just using transients slow down your website you should check the setup of your hosting.

For reference see an example on my own website which should not be slow at all even with a lot of images on a page (maybe the first load of all the thumbnails takes a moment, but reloading it multiple times after that should be quite fast): https://arnowelzel.de/en/england-2017 – at least https://tools.pingdom.com/ reports a loading time of only 1.9 seconds.

However, I use Redis object cache which also covers transients, maybe this is an option for you too.

The only alternative would be not to cache any image meta data at all – but then it would be even slower since all image meta data (size, EXIF data if available, captions) would have to be retrieved from the image files and the WordPress database with every single request.

I can add an option to disable meta data caching in transients, but I doubt, that this will change a lot – because file operations on the server will still happen for every image then.

Release 5.1.7 adds an option to disable using transients to cache image meta data – but since the plugin then needs to read the meta data from the images all the time, it may still be slow, even if you disable that option.

Thank you for your answer and the option to disable transients, I will test this and report.

The problem is, that I have a big blog with tens of thousand users every day, over 70.000 images and several thousand articles (some of them with hundreds of thumbnail-pictures in them). Since the blog is, lets say “organically grown” over the years, there are several things speed-wise, that might not be ideal, but the hosting itself shouldn’t be the problem.

We use nginx cache with our hoster Raidboxes and also use Cloudflare, so I don’t think it would be a good idea to use another Caching System, but since I am not that tech-savy, I don’t really know what impact that would have.

I also maintain websites with high volume access (for example a film festival which has more then 100.000 visits per day and at some times also more than 100 requests per second, when the festival is ongoing) where also my plugin is used for picture galleries with many images.

Since that website also uses PODS and a quite complex backend logic to build the daily movie program, I created a custom backend caching solution which creates static snapshots of every page similar to Cachify which is unfortunately not updated for a while – but the way how that works, did not change, even in the latest version of WordPress. This way the page loading time can be reduced to about 0.1 seconds even without any other cache at all (no NGINX, no Cloudflare). The caching is not very complicated – just on additional function in the theme and a backend menu to be able to clear the cache if needed. It’s just not useful to publish this, since I don’t have time to support this for many users.

Also Linux itself, PHP-FPM (static pool vs. dynamic etc.) and the database configuration can have a big impact on how good or bad WordPress runs on a server. If you want to know more about this, just let me know – you can also contact me via e-mail (see https://arnowelzel.de/en/about-me).