Systems and methods for improving the performance of a data storage and retrieval system by enabling dynamic switching from one internal data structure to another in response to detecting conditions indicating that a switch would improve performance. In one embodiment, a network proxy implements a cache using a first internal data structure. The caches objects comprise Web pages, and the cache keys comprise URLs corresponding to the Web pages. The proxy monitors cache usage and periodically determines costs associated with usage of the first data structure and an alternative data structure. If the costs associated with the alternative data structure are less than the costs associated with the first data structure, the proxy crates the alternative data structure, migrates data from the first data structure to the alternative data structure, begins using the alternative data structure for the cache, and deletes the first data structure.