The process consisted of 4 interviews First it was a screening with HR.

Simple and classic questions.

Where are you currently working ?

Why do you want to join us ?

Do you know the company ?

What are you willing to do in your next job?

And more.

If you succeed, they'll send you a Codility test with 3 exercises.

One is easy and the other two are medium.

Not too hard, but not too easy as well.

After the Codility test there's a call with two developers.

They'll present you a simple exercise and start debating about it.

There's not a right answer here.

They're trying to test if you ask questions, if you can assume other stuff.

They'll ask questions about the exercise and about the code.

Like, "What is the difference between Integer and int", "What are the different types of exceptions and subtypes?" (checked vs unchecked) "Would you prefer Optional values over exceptions for handling certain types of things?"

The algorithm to design was "return the two biggest elements in an array"

Finally there's a system design interview.

They present you a solution and they expect you to discuss it.

They want you to talk about whether it's necessary to have a queue and which would fit if that's the case.

Difference between commands and events.

Sync and async.

In my case the idea was a system that gave a flower to each new subscriber because they wanted to promote the app.

A simple design was presented to me and I had to talk about pros/cons and what I would do differently if needed and why

Everything is explained in detail above.