Designing DynamoDB Global Secondary Indexes requires understanding your access patterns upfront. This article walks through the GSI design for a blog platform: by status (draft vs published), by author, by tag, by slug, by tag metadata, and by recency (updatedAt). We cover sort key design, projection types (ALL vs KEYS_ONLY vs INCLUDE), and how to handle sparse indexes. The article also discusses cost implications of GSIs, capacity planning, and how to backfill new GSIs onto existing tables without downtime.