The worst interview experience. First, there was a discussion with HR and the technical manager. Then came the assignment. You are expected to write a solution for this assignment in 6 hours, but the scope is vast, and they want a complete and optimal solution—remember, you’re doing this in your spare time and unpaid. They set a 3-day deadline for the assignment without inquiring about your availability. After I submitted a solution using Clean Architecture, DDD, Redis, and Docker, I received this feedback: With this wallet implementation, double spending is only prevented if only one provider is integrated. If more than one provider is integrated, double spending could occur across providers. Every time the wallet is queried, the entire transaction stack for the user is read from the database/Redis. This is not optimal from a performance perspective. They didn’t even mention the external providers, and of course, with all the tests in place, these edge cases can be covered. I was aware that all transactions were queried; this was primarily for testing purposes. In production, you would implement pagination. I want to warn other candidates not to waste their time on this assignment. You will spend significantly more hours crafting a solution that they might not accept, and they will still be dissatisfied, leaving you with many unpaid hours of effort. They should provide you with a chance to explain your solution and how you would improve it. It is unrealistic to expect a full solution in just 6 hours. I have over 10 years of experience, and I have never had anyone reject my assignment without a discussion. Even if I were to implement something like this for my job, it would take considerably more time.