That's probably Firefox's own Firefox Multi-Account Containers[0]. Groups caches/cookies into designated categories for each tab (personal, work, shopping, etc.), with smart recognition for assigned sites.
Someone should do a study on the performance impacts of using something like this on all sites for various kinds of "typical" web browsing profiles. I'm honestly guessing a lot of the losses would be in the noise for me personally.
There is an additional Firefox extension that integrates with multi-account containers, Temporary Containers. This is highly configurable - I have it create a new container for every domain I visit, with a couple of exceptions that are tied to permanent containers.
I run that on my personal devices.
At work, there is so much in terms of SSO the amount of redirects that happen mean that temp-container-per-domain breaks all sorts of workflows, so I go without on the work machine.
I notice no major difference between these two configurations, although I'm sure that there would be things that are measurable, though imperceptible.