To evaluate the effectiveness of the recommendation engine at Netflix, I would employ various metrics that reflect both user engagement and business performance. One important metric could be the click-through rates for recommended items; a high click-through rate would suggest that the engine is offering relevant suggestions. Likewise, conversion rates are vital to assess whether the recommendations prompt users to watch the suggested content. Additionally, watch time serves as a significant indicator of whether users are engaging with the content they were directed to. On a broader strategic level, examining the growth in average customer lifetime value could provide valuable insights into whether the recommendation engine is enhancing user engagement and, consequently, boosting revenue for Netflix.