CACHE_
Number of slots in the primary (Tier-1) fast cache. Must be a power of 2 so that key and MASK is a fast modulo.
2048 slots @ ~12 bytes per entry ≈ ~24 KB (keys) + ~8 KB (values) = ~32 KB total. Hit-rate analysis: typical app has 100–300 distinct dimension configurations; 2048 slots gives <15% fill ratio under normal usage — near-zero collision rate.