Not OP, but I imagine this is fairly language specific. This is where Java shines. Keep in mind I mostly work with services not applications. My process looks

Not OP, but I imagine this is fairly language specific. This is where Java shines. Keep in mind I mostly work with services not applications. My process looks like this: Step one: Identify sources of reflection, this is the triskyest. Hopefully the only dependencies are open source, so you generally know what they do and grep can usually find the rest. Step Two: go code spelunking. Find your entry points. Find your main() or framework equivalent. Find callsites for rest endpoints, rpc, jmx, etc. Step three: find other "external request processing" endpoints. Do you have timer threads? Reading a Kafka stream and acting per record? Etc. Once you understand those, you can interpret where most any stacktrace is from. Good old Intellij or Eclipse can give you all the callsites for a functions as you root around. You should slowly get a feel for which part of the code things get called from. Now start asking questions like: what data is shared between these entry points? What's mutable? Is it all done safely? Hopefully this wasn't too narrow an example. I'd imagine it'll apply to any services.