Lemma 10.122.5. Let $R \to S$ be a finite type ring map. Then $R \to S$ is quasi-finite if and only if for all primes $\mathfrak p \subset R$ the ring $S \otimes _ R \kappa (\mathfrak p)$ is finite over $\kappa (\mathfrak p)$.
Proof. Follows immediately from the more general Lemma 10.122.4. $\square$
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