Blip (Portugal) Software Engineer, Backend interview questions

Overall I think that it was a good interview, I can consider that the company is very demanding regarding the interviews and its a long process. In my case it had 4 stages: 1. 30min phone call with HR 2. Devskiller test, wich has question of multiple choices regarding a lot of stuff about OOP and Java, things like Garbage Collector, design patterns, etc and at the end it has a small pratical exercise to code, it wasn't any difficult at all. 3. 45 min of technical interview with 2 developers, in here we talk about a bit of my developer journey, my experiences and then it followed up to a lot of questions about OOP and Java, such as access modifiers, synchronization, java collections, immutability, etc. In my opinion it wasn't hard at all, just need to know the concepts. 4. final interview. 2h technical interview with another 2 developers (in my case it involved an extra one just observing), we covered things like the interview before my experience and a few questions about Java and OOP this part was about 1 hour and then we moved to a pratical interview where they gave me a problem to solve and analyze time and space complexity, the problem wasn't hard either and finally a question about system design wich for me it was the more difficult part and wasn't very confortable at. At the end of this interview it followed up for more 30 mins with HR for more social questions. Overall despite the number of stages and the amount of hours, I think the staff was very friendly and it isn't to hard.