The site_transient_update_{$type}s filter doesn't scale

[Chouby]

On my local test install, I noticed that, when Polylang Pro was activated, the plugins list page was very slow. The load time was about 20s for around 300 plugins. The issue was coming from our class PLL_T15S which is an adaptation from your project.

I narrowed the issue to the calls to wp_get_installed_translations() and get_available_languages() which are called once per plugin and become very expensive when there are a lot of translation files.

I fixed the issue in Polylang by making sure that these functions are called only once for all plugins. See my commit: polylang/polylang@6f9814b. The page load time decreased from 20 s to 2 s.

Hope it helps.