Counterpoint, I made a recent shift to Android from many many years of iOS development. It's not the language that I struggled with, it was the completely diffe

Counterpoint, I made a recent shift to Android from many many years of iOS development. It's not the language that I struggled with, it was the completely different engineering culture surrounding the platform. Yes there are many similarities, things like concerns for battery life and thoughtful network usage. However, that's where the similarities end. The APIs and appropriate architecture decisions are completely different, so I needed to build all new instincts. Then, you have the tooling that are completely different. Where it would normally take me 5 min to jump into Xcode to profile an application, inspect for leaks or other performance issues, I spent a few hours going through Android documentation learning how to do the same thing. Last, and this one is a bit nuanced and sort of hard to explain. As a senior engineer, you're typically expected to help mentor others and maintain the foundations of your product so that as new people join they have a template to work from. If you're switching to something so different, you could end up hurting the team (or company) by using the wrong patterns and promoting incompatible ideas. People need to trust you and if you break that trust at the beginning of your employment, it'll be really hard to earn it back. No regrets though, and I'm grateful to my employer for giving me the space to make the shift. However, I do not believe in the idea you can hire someone at a generalist level and then expect them to be productive anytime soon. There is a saying, "Jack of All Trades, Master of None," and although very cynical, it's just an honest statement when it comes to these things. Hire the right person for the role you need filled first, then if you want to make room for engineers who are looking for big career changes, make sure your product and team won't suffer for that and you have the right culture in place to encourage that kind of growth.