Very easy for senior engineers.

I have known and been at places where there is always a scarcity of senior engineers. Not someone fresh out of school with zero work experience, but someone with actual working experience and have shipped products.

If you have 3–5 years of experience under your belt and review some fundamental algorithms just to prepare for the interview, it is very likely you will get many offers.

With that said, companies do look for person who are cultural fits as well. But the bottomline is that, senior engineer is always in need.