The theory is that because Dark offers a nice interactive environment when you have a request come in you can inspect the data, "fix up" your code, rerun it quite smoothly. Completely removing the deploy question. Really good for glue projects IMO. Think stuff like google scripts (though google scripts are much more miserable to ues)
Many moons ago I had tried to play with Dark and unfortunately the surrounding language stuff really didn't work out for me though. I really liked the concept but ultimately I think I would have preferred if they had just built out the environment on some other language.
Even just lua would work decently well for their use cases, if paired with a good "standard" library.
The UI was fun to use, in any case.
EDIT: to be clear I'm a bit of a type weenie but for the stuff Dark could be good with you really sometimes just want to look at the JSON and poke at it, and your type systems aren't going to be helping you _that much_
I don't understand. Hot code reloading on my dev laptop gets me this kind of quick iteration when I'm solving problems. But why do I want that in production?
A user send a request, and gets a response you don't grasp. In Darklang-like envs that request data is held onto for a bit, you can replay it and tweak things. And you don't have to think about environment differences because you're working _in production_.
You could be taking webhook values from some external service that starts passing in unknown values. That service's documentation might just be outright wrong about its behavior. But you don't have to play post-mortem forensics, as you can hold onto information.
This can be valuable for one-offs where you don't mind breakage, with relatively low request coutns and "time to fix" is what you're optimizing rather than general uptime/downtime. So some silly discord bot could work off of this, but you probably don't want your B2B SaaS being in cowboy mode.
Sometimes you want a thing that just does something and you don't care about how busted it is, but you want it to be _very easy_ to fix up issues you do care about.