Disk and Memory can both be bottle necks, however with compression on Roaring bitmaps you typically keep your entire index in memory and compute in a compressed

Disk and Memory can both be bottle necks, however with compression on Roaring bitmaps you typically keep your entire index in memory and compute in a compressed state, avoiding slow disk. You do in fact become CPU bound on queries, even intelligent multi-threading, and CPU efficiency comes into play (especially so as a bitmap begins expanding across several shards).