Revolut Sr Software Engineer interview questions

Got a home assignment prior the first interview. It's common practice and it's ok. But it's been reviewed by them late in the evening. Being asked to do some additions to the assignment and the Interview was appointed immediately after my current job's working hours. Am I supposed to improve my assignment at night? Was a red flag for me implying that they like working in the off hours.

Just some standard Coding Challenges mostly focusing on speed and slightly on correctness too. If you work for a while to prepare your coding speed then you will find it easy mostly. However, they do ask you regarding Multithreading so you gotta have those concepts very clear beforehand.