Mobile Development - I have 5 years of mobile development experience, having worked as a software engineer.
React Native and Firebase changed the mobile development game entirely – everyone can now launch a fully-fledged mobile app in no time. Even those who are just learning how to code.
The combination of these two (React Native & Firebase) has lowered the barrier of entry into the mobile world tremendously. You get to build an app for both iOS and Android, with the same code, while not having to deal with server infrastructure and backend development. If you developed mobile apps 5 years ago, this probably sounds too good to be true.