Explain horizontal vs vertical partitioning and partition strategies.

Vertical partitioning splits columns across tables (normalize or separate hot/cold columns). Horizontal partitioning (sharding) splits rows. Strategies: Range (by value ranges - time, ID), Hash (consistent hash of key - even distribution), List (by explicit values - geography), Composite (combined). Consider: query patterns (avoid cross-partition queries), data distribution (avoid hotspots), rebalancing needs. PostgreSQL has declarative partitioning; application-level sharding for cross-node.