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.