Flow Traders Software Developer interview questions

First there was a Hackerrank test with time constraints. General C++ and algorithm problems. There were some challenging ones among them. After I passed the test, there was a phone interview with HR. In the phone HR insisted on finding out whether I know how FlowTraders profit and what ETP is although it was stated in the job description there is no prior financial knowledge required. Anyway, then there was a codepair with a person from the company. Person who interviewed me was looking very tired and inpatient and it seemed like that s/he just wants to get over with the interview. There was a very specific question about multithreading and an algorithm question related with string operations. I did not know the answer to first knowledge question, I was upset and unable to come up with a good solution to second problem. After two weeks they told me that I am below standard.