Although my recruiter cleared the whole process, I just want to know what are the expectations in the onsite product/API design round?

My recruiter gave me 2 options -> Product Design and Architecture Design. Architecture Design seemed like System Design and I am sure I am not prepared for that. So, the recruiter suggested me to go with Product design saying that in this you have to just design the APIs.

I am still not very sure what will be asked in that round, how to prepare for it, and what will be the expectations in that round. I will highly appreciate it if anyone assist me with this.