1. Screening with recruiter Questions about my background, with some technical questions just to check if I'm familiar with basic required things. The recruiter gave very detailed information about what to expect from the tech interview, which topics might be covered and what kind of questions might be asked.

2. Technical interview Coding challenge. I was asked to implement a simple in-memory load balancer for a pool of IP addresses. Then the requirements changed to add different balancing strategies. Another time, I was asked to implement a URL shortener service. In this interview, the focus should be on TDD, patterns, SOLID, and clean code.

3. Technical interview I was given a code snippet, an Account class and a service with a transfer() method, where I needed to implement the transfer logic. In this interview, the focus was on thread-safety, concurrency, and DDD. First, I implemented with pure Java locks (ReentrantLock), then with an option for a DB lock. I implemented a pure procedural SQL implementation. There was a deep dive into transaction isolation levels, anomalies, and optimistic/pessimistic locks. Also, in a previous interview, I was asked about resilience/stability patterns, microservices, and DB indexes.

Overall, my impression is that they don't have a high need for engineers, just looking if some genius guy who doesn't make any mistakes while coding in the interview and answers all questions 200% correctly exists. If you lose attention and make a couple of mistakes, you'll fail the interview.

I felt like I did well in the interview, but was rejected both times. As I said, small mistakes, and you are done.

Implement load balancer. Implement URL shortener. Implement money transfer method, making it thread-safe and performant.

Key concepts: Transaction isolation, Optimistic/pessimistic locks, DB indexes, Thread safety, Stability/resilience patterns, Distributed transactions, Event sourcing, Domain-Driven Design (DDD).