This is again down to XOR, yes cache will kick in fast on that route (closer to destination route becomes more unique, i.,e a single cache hit), but there are separate individual routes to a chunk. Each of these will cache for 10 mins (current) but the app needs to be super popular to hit a cache and then only for 10 mins or so (also based on number of cache hits per route). So popular apps will get paid a lot and cache hit a lot too. So now imagine several popular apps, they all get the same chance and maybe by almost constantly cached and then this not so much used app, it all converges nicely, perhaps.