Revolut Interview Question

Develop a Service Registry using TDD. It can only have 10 records, and no duplicates. Then implement a get() method with 2 strategies: random and Round Robin. Develop a method which receives 2 accounts and makes a transfer. Has to have into account concurrency. Then following debate about SQL statements to make it concurrent, isolation levels, optimistic locking, indexes in DBs, DDD, CQRS, distributed logging, monitoring.