The key is a deterministic hash of email + product — same email always produces the same key for that product. It's an identity marker: "this email has been issued a license for MyBooks." Nothing else is baked in.

Everything mutable — update-support expiry, seat count, purchase amount, renewal history, block status — lives server-side in dbo.purchases / dbo.blocked. The client app calls the API on every activation + update check to get the live state.

That means you never need to re-issue a key when someone renews, adds a seat, changes their password, etc. — it just keeps working. Resending the same email/key pair to a customer who lost their receipt is the normal recovery path.