Whether you’re coming from the Android world or not, you’ve probably heard about Kotlin (the programming language) and its asynchronous programming concept called Coroutines. It’s a neat concept that helps you create execution blocks similar to light-weight threads, while at the same time allowing you to write your asynchronous code in a synchronous fashion.

On the other hand, many of us got really (really) used to Reactive Extensions in many languages, and we prefer to go down this road. With ReactiveX, you can chain your asynchronous blocks in future-like structures, and easily control threading around them.

Well, you know how it usually goes - you read about something (aha! what is this coroutines thing)… maybe you see a couple of talks on the topic, maybe you get interested. After you try it out and decide to use it in a real project, you start typing your code… and boom! Your program crashes. You then go to StackOverflow to check for answers to your problem, and surprise: you’re not handling errors properly. You copy-paste the solution without any edits or tests and you’re ready for release.

Hopefully this is not you. You want to check everything before using a new language or library, you want to fully understand the consequences of switching over to a different solution from the one you currently have. There are some quirks in every approach, sure, but do you know all of the corner cases?

That’s why we need to have this talk. Let’s go together through the most interesting examples of how we can get (and handle) errors with ReactiveX and Coroutines.