KV Cache Quantization Is 4× Slower on My Mac and 28% Faster on a Rented L4

The same idea — store attention keys and values in fewer bits — measured on two stacks: MLX's --kv-bits on an M3 raises RAM and slows decode 4×, while vLLM's fp8 KV cache on an L4 doubles capacity and speeds decode up to 28%. KV quantization is a property of the implementation and hardware, not the technique.