I am debugging a custom CMS made with Symfony (3.x) using Blackfire, in order to improve the performance as much as possible (and learn!). I already removed all heavy constructor services (Doctrine, Twig/Templating) from event listeners/subscribers, but there is one which I can't (or maybe shouldn't) remove, since it's in core. I am talking about Symfony\Component\HttpKernel\EventListener\TranslatorListener, which has "translator" service as dependency, and that service has a heavy constructor. It takes ~10% of the time in my current best case scenario.

I was looking for some issue similar to this, to no create a duplicate, I found some others about improve it (i.e. limiting some loaders/dumpers), but I didn't find any issue about lazy-loading that service (or its heavy logic) to avoid its construction at all unless required.