How to measure cache performance?

What customer metrics does Amazon use to measure its performance?

• I was recently reading this article on Forbes : http://www.forbes.com/sites/georgeanders/2012/04/04/inside-amazon/ which touches on the 500 metrics or so that Amazon uses to measure its performance. Any insights into what these are? Quote: " Amazon tracks its performance against about 500 measurable goals.  Nearly 80% relate to customer objectives. Some Amazonians try to reduce  out-of-stock merchandise. Others race to build a bigger library of  downloadable movies. Intricate algorithms turn one group of shoppers’  past habits into custom recommendations for new customers. Hourly  bestseller lists identify what’s hot. Weekly reviews keep track of who  is on course—and where corrective attention is needed."

• Answer:

  Here are a few I remember: Contacts per unit: for inbound contacts to the call center. Up is bad. In stock, inactive: If the piece of inventory is in stock, but not "merchandised", then it's not sellable to the customer. Up is bad. Inventory record defect rate (IRDR): this has to so with a random inventory count, where the virtual is matched with the physical in a bin. Up is bad, meaning that if IRDR is high, then a picker could be sent to a bin to pick a unit, but it won't be there. Downstream implication is that the shipping cut off could be missed because amzn now has to chase that unit from elsewhere. Fasttrack misses: this measures the % of units or shipments that miss the cutoff time. There's a bunch more, but you get the point. I'd say most of the customer metrics have to do on the fulfillment side and CS, and Bezos is fanatical about fulfillment and supply chain and CS - I'd say more so than anything on the front end or storefront. At least when I was there.