Here’s my 30x success story: Julia's applicable context is getting narrower over time? - #5 by Satvik , as someone with years of experience with numpy and ~0 experience with Julia at the time.
Currently I find that Julia really shines anywhere you have a memory bottleneck. It’s also worth noting that profiling is significantly easier in Julia, because it’s “Julia all the way down” – so even in cases where I could achieve the same speedup in Python, it was much easier to find that speedup in Julia.