“…While the analysis becomes more complex for flexible and advanced caching methods, bounds for optimum caching efficiency have been derived from Belady's bound to general min-cost flow and knapsack solutions, which fully cover scorebased strategies [4][7] [11][19] [58][59] [92][93] [112] [116]. Time-to-live (TTL) caching emerged as another branch of strategies for web applications, where each object in a cache is valid only for a limited time.…”