Walk me through the backend architecture of an AI product.

"The overall process was too long. Reached out by the recruiter at the end of May, Hiring manager screening at the beginning of June, then being ghosted for almost a month, got recruiter's email for the next round, which is a take home assignment (AI prototype). Presented my prototype with hiring manager and a SW engineer at the beginning of July, and complete 4 final rounds at the end of July. Added one additional round for technical at the beginning of August, and ghosted by the recruiter again. I heard from another recruiter that the roles was filled so I assumed I was rejected. Most of the interviews are just like the typical PM interview, no PM case except for the AI prototype assignment. I didn't do well on the technical and the skip level interview. The skip level interview was suppose to be a cultural fit interview but it turned out to be a technical interview so caught me off-guard. All technical interviews (+ the skip level one) asked deep technical question."