The sharding key is the heart of any sharding strategy. A poorly chosen key can lead to uneven data distribution, creating ‘hot spots.’ For instance, if you were to shard a global customer database based on countries, and a vast majority of your users are from the US, then the shard containing US data might get overwhelmed. A 2020 study on database management found that 40% of sharding inefficiencies arose from suboptimal sharding key selections.
