Not a bad article, but I wish they'd focus on search latency instead of thread pool size. Define your required 99.999th latency, draw a line on a chart, and tune/scale to reach it. If that requires SSDs, so be it. If you can reach your latency goals with huge thread pool spikes, fantastic.

Internal operational metrics like thread pool size are excellent for diagnosing failures to reach target latencies, but keeping thread pool queues low shouldn't be the direct goal.