The association between very long response time (VLRT) requests that from latency long tail, and transient resource contention called millibottlenecks, has been established for n-tier web-facing ap-plications, including CPU, memory, and disk. However, how much of latency long tail problem can be explained by millibottlenecks? Using sophisticated performance log data management tools, and teamed ma-chine learning classifiers, this paper shows strong association between hundreds of VLRT request clusters (the latency long tail) and millibot-tlenecks in every kind of server and all their resource types. These promising results suggest that the Millibottleneck Theory may explain most, if not all, latency long tail phenomena.