A set of features is identified in a resource provided from a Content Delivery Network (CDN), a feature causing a first information available in the resource at a first time to change to a second information in the resource at a second time responsive to an event. A set of weights is determined corresponding to the set of features. A weight is related to a corresponding feature in the set of features. Using the set of weights and the set of features to compute an entropy comprising a probability that the resource is going to change. Using the entropy, a stale probability is computed, comprising a probability that an outdated version of the resource is going to be served from a cache in the CDN at the second time. A refresh information is adjusted responsive to the stale probability exceeding a threshold probability.