Daily micro-tips for C#, SQL, performance, and scalable backend engineering.
Created an index but your query still takes 30 seconds? SQL Server might be ignoring it due to implicit conversions, functions, or wildcard positioning. Index Killer #1 – Functions on Indexed Columns: — Index exists on CreatedDate CREATE INDEX IX_Orders_CreatedDate ON Orders(CreatedDate); — ❌ BAD: Index ignored, full table scan SELECT * FROM Orders WHERE […]
Indexes are not magic. Bad case Low-selectivity columns Over-indexing Diagnosis SET STATISTICS IO ON; Why Wrong index = more lookups than scans.
Too many indexes = slower writes. Why Every INSERT/UPDATE must update all indexes. Rule Indexes are not free. Audit sys.dm_db_index_usage_stats