HANDLING HOT SHARDS

Summary from the TLDR Data newsletter

Sharding by tenant ID works until a large tenant makes one shard run hot, as Slack learned when enterprise workspaces overwhelmed workspace-keyed shards. The fixes range from vertical scaling to isolating whale tenants on dedicated shards and ultimately resharding tables by the column queries actually touch. Choosing keys per table rather than globally keeps common access paths single-shard while spreading load.