Booking.com Software Engineer interview experience

The prompt defined transactions with a type (PAYIN or PAYOUT), a currency code, and an amount, plus an additional currency c value that fed into the rules. The discussion quickly became about correctness and assumptions rather than just writing code.

I got pulled into detailed questions like whether the payout fee was fixed or varied based on how much currency was exchanged, and what the payout fee units were. We also discussed whether conversion rates were provided or if I’d need to reason about them abstractly. Another big theme was sequencing—whether the transactions had to be processed