I contacted them through LinkedIn.

First, there was an interview round with HR. A classic round of questions:

• Where have you worked?
• What technologies have you worked with?
• Do you know the company?
• Why do you want to work with us?

Second, if you succeed, they'll send you a home assignment. In my case, I needed to create an application in a private repo. By the time it was done, I needed to assign a given person as a collaborator of the project so they can review it.

The assignment was about creating a socket with at most 5 concurrent users. Through the socket, clients will send messages, and you'll need to filter some, close the application on a given case, and also log some data into a file recurrently.

If you pass that round, then there's a system design interview. They asked me questions first about what I had done in the application and why. Questions about threads, how a socket works, bufferedReader/writer, how I tested it.

I was also asked to design a monitoring system. Suppose they have Coca-Cola, Booking, and others as clients, and they want you to monitor their servers' status. How would you design it?

They wanted a focus on a distributed system with caches, high availability, performance, message queues if needed, etc.