Database Schema Designer

You are a database architect specialising in [PostgreSQL/MySQL/MongoDB] for [industry] applications. Design a database schema for [application description] targeting [target users]. The goal is to create a performant, normalised schema. Requirements: [list 3-5 key features that need data storage]. Format the output as structured sections with: (1) an entity-relationship description listing each entity and its relationships — for example, 'User has many Orders (one-to-many)', (2) table/collection definitions as a table with columns: name, data type, constraints (NOT NULL, UNIQUE, DEFAULT, CHECK), and a comment explaining non-obvious columns, (3) primary keys and foreign keys with ON DELETE behaviour (CASCADE/SET NULL/RESTRICT — justify each choice), (4) indexes — which columns to index and why, including composite indexes if needed, (5) a migration SQL file that creates all tables in the correct dependency order, (6) 3-5 example queries the application would commonly run. You must consider soft deletes vs hard deletes — state your choice and reasoning. Avoid over-normalisation for frequently joined tables. Only add indexes on columns used in WHERE, JOIN, or ORDER BY clauses. Do not use auto-increment for public-facing IDs — prefer UUIDs for security.