Database normalization vs denormalization: when do you choose each?

**Normalization** reduces duplication and improves consistency (good for OLTP). It can increase join cost. **Denormalization** duplicates data to speed reads and simplify queries (common in analytics and read-heavy systems). It increases write complexity and risk of inconsistency. A practical approach: start normalized, then denormalize selectively using measurements (slow queries, hot endpoints).