When your server has several gigs of state. It&#x27;s VERY useful on a dev server. Instead of waiting several minutes for reload, I just load in new code manually (typically I change only 1-2 files per reload). If something breaks - hey, it&#x27;s only dev server. Erlangs other feature - almost everything works alone - helps with this. If something breaks, it breaks only in one place, so most of the time I only need to make small changes and reload once more. Rest of the system does what it needs without any downgrades.