The interview process consisted of three parts:

• An initial screening call (approximately 30 minutes).
• A live coding exercise (approximately 1 hour).
• A final interview, which also included a live coding exercise (approximately 1 hour).

The initial call was with a member of the Revolut recruitment team. It covered general questions and some more technical topics, such as SOLID principles and the cost of retrieving items from a hashmap.

The first coding exercise was with a backend engineer. The task was to implement a URL shortener. This exercise was split into sections, with new requirements added after completing the previous one. This made things a bit tricky, as I initially implemented things one way and then had to rethink. The focus was on ensuring the code was correct and passed tests at the end of each section.

The final interview began with another coding exercise, followed by a set of questions about database transactions and concurrency.

The coding exercise involved implementing a method for moving money between two accounts, with a focus on making the solution thread-safe. This served as the context for a conversation about concurrency in code and database transactions.

Additional questions covered database transactions, ACID properties, and isolation levels.

This was quite a challenging interview process for me, but it was interesting. Everyone I interacted with was very friendly and professional, which made it less stressful, even when I knew I was getting some questions wrong.

In the end, I was offered a more junior position as they didn't feel I had the right skillset for a senior role. There were no open positions for junior staff at the time. However, within a week, I was contacted about a suitable position and had the chance to speak with a hiring team member to ask questions.

The offer I received was quite good, but I decided to decline due to personal circumstances. I think I would apply again in the future if things change.

Which is the most important of the SOLID principles?

What are the different isolation levels for database transactions?

Can you explain what ACID means?