Alexander Ioffe: Why is my Whale Query 1000x Slower in Prod? Databases hate skew, each hates it differently
Ten enterprise customers own 80% of the orders. On uniform test data the query runs in ~1ms; on that real skew it runs ~1,000x slower. The fix doesn't transfer between engines: Postgres is rescued by one free session setting, SQL Server can't be touched by it and needs a completely different…