Like others have already mentioned, that's a developer who saw the blood on the walls. They've likely seen this issue before and know the signs to look out for.

Like others have already mentioned, that's a developer who saw the blood on the walls. They've likely seen this issue before and know the signs to look out for. It doesn't make them any smarter but it does mean they are wiser/more experienced with this tech stack. As a personal example, my team sees me as the consult for all the arcane fuckery that you find as a result of unusual C++ behaviour or build system issues. This doesn't make me a good dev but it does mean that I've been through my paces there and bled my share. But at the same time I'm practically a blind, helpless child wrt most of the JVM or web tech stacks. IMHO my colleagues are wizards for being able to make heads or tails of issues in those spaces. Point being, this isn't a matter of "Oh I could solve that in seconds", it's a matter of "Oh god I remember dealing with this type of issue. Here's the cause and how to fix & avoid it".