[rufius]

With regard to your last comment about hiring senior devs with experience in the stack: I would say it depends on what you're hiring for and your long term vision for your team I think.

In my team's case, I was hired to do ML/BigData but had no prior experience. My boss's philosophy is that he wants smart engineers with a desire to learn more than he wants area experts. He's been burned more than once with area experts who were unable to pivot well with the shifting priorities of the team.

That said - if you're hiring someone to come be your ML expert then that requires an expert. Tech stacks are less that way in my opinion and they're rarely static. Even the debugging and troubleshooting tends to be similar if you know the problem space.