I’ve designed a star schema for Facebook Marketplace with the following tables:

dim_Users – Users on facebook(buyers)

dim_Listings – Marketplace listing details

dim_seller – Users(sellers) who created listing

dim_Date – the mandatory date dimension

fact_Transaction – Table for tack transaction between buyer and seller(This table will only have entry if we conclude that product was sold to some buyer).

Attributes:
is_business_acount( This field is to track whether seller is running small business from home, this can be calculated by total active listings a seller has. If total listings are greater than certain threshold, then we can assume it’s a small business. I’ve added this field to ignore outliers while calculating certain metrics)

I have below concerns-
Can I use user_id as PK for both Users & Seller table? (Seller has to be facebook user to create listing)

Number of records in my fact table will be <= number of records in listing dimension table. Is that ok?

Please let me know if this design make sense. Suggest any optimizations or improvements?