Zipf's law.

the two-minute refresher

• Rank 1: 1000 req/s, rank 2: 500, rank 3: 333, rank 4: 250.
• Real traffic is skewed, not uniform: plan for the head of the curve.
• Good news for caching: a small cache holds the hottest items and gets a high hit ratio.
• Bad news for partitioning: the top keys can overload their shards.