Early in my career, I saw many examples of homegrown AB test frameworks, event tracking frameworks, alerting tools, monitoring tools, etc. Now it seems like everyone just buys LaunchDarkly, Segment, DataDog, etc. Other than admin panels, I have a hard time thinking of any truly "internal" tools at my last few companies (FAANG was the exception, but they are big enough that I think it genuinely makes sense for them to build their own tools for things like applicant tracking, meeting booking, etc).
Maybe I'm just forgetting something - do other ppl have examples "internal tools"?