A method, computer program product, and system for migrating URL data objects in a proxy server array when an array member is removed, added, or temporarily unavailable. An array membership list containing array membership information is available at each proxy server in the array and at all enabled client that is used in conjunction with the URL as the information for identifying the correct proxy server where the URL data object resides. First, a deterministic hash value is computed for each proxy server name and the URL. Next, a combined hash value is computed that combines the URL hash value with each proxy server hash value. Finally, the proxy server with the highest "score" or combined hash value is identified as the proxy server where the desired URL data object should reside in local cache storage. Since the array membership list, the URL, and the hashing algorithm is the same at each proxy server or enabled client, the same proxy server will be identified as having the URL data object regardless of which proxy server originally receives or enabled client generates the URL data object request. The hashing algorithm is designed to automatically compensate for changes in the array membership list so that only the fewest amount of URL data objects will migrate from the local cache of one proxy server to another proxy server as a result of array membership changes.