The thread is quite old. A lot has changed since then. Of course, invalidations are still relevant but SnoopCompile.jl got major updates in between.
Just to be sure, the first step should be profiling with @profview or similar tools to see the lines of code most time is spend. Even if runtime is fast, it might give an indication.
Once you go into details, then SnoopCompile.jl, JET.jl and Cthulhu.jl are useful. See also Optimizing your code .