Spring Reactor common mistakes

I recently gotten fond of Spring Reactor, reactive java library used by Spring 5.0. There is a lot of resources out there which describe it, so I’m not going to repeat the internet here. But in short it makes any asynchronous development a LOT easier and I dare to say its the first library which makes it almost trivial. There is a catch, learning curve is steep. And when I mean steep I mean it took me at least half a year (senior java dev) to wrap my head around it. Me and my colleagues made some stupid mistakes so here are 4 so far, will add more in the future.