__builtin_prefetch is what memcached and Redis-style hash table implementations sprinkle into bucket-chasing code to hide the ~100-cycle DRAM latency the hardware prefetcher can't predict for pointer-chained data. PostgreSQL's B-tree index scans and RocksDB's block reads use the identical trick, since getting the prefetch distance right can turn a 30-40% slowdown from cache misses into a near wash.