Define the question the model answers
Start with Product queries: which supplier fields must be available when reading or presenting a product? Store only those fields and retain a stable supplier identifier.
The name SupplierReadModel communicates purpose. It is a query model in Product, not an alternative write API for Seller.
Treat projection updates as a contract
Messages or other explicit synchronization contracts carry changes from the owning service. Consumers need a defined behavior for duplicate, delayed or out-of-order updates.
A version or ordering rule may be appropriate, but it must come from the real contract. Do not invent sequence guarantees that the transport does not provide.
Plan recovery as well as normal delivery
A projection needs a way to be reconciled or rebuilt when it is missing data. Decide how to observe lag and how a query behaves before the supplier record arrives.
For critical operations, validate authoritative business facts at the appropriate boundary. A read model reduces coupling; it does not make consistency requirements disappear.
Further reading
Primary documentation & specification