Leverage database-specific features to optimize queries and improve performance. Different database engines have unique capabilities that can significantly enhance query efficiency when used appropriately. For PostgreSQL: - Use `ANY` operator instead of `IN` for queries with large arrays of values to improve query plan caching - Handle joins in UPDATE statements properly to avoid unnecessary subqueries - Consider PostgreSQL-specific data types (arrays, JSONB) for more efficient storage and querying For example, with PostgreSQL: ```ruby # Rails can optimize this to use PostgreSQL's more efficient ANY operator: User.where(id: large_array_of_ids) # SQL: user.id = ANY('{1,2,3}') instead of user.id IN (1,2,3) ``` When updating with joins, be aware of database-specific limitations: ```ruby # PostgreSQL supports UPDATE with FROM for inner joins Post.joins(:author).where(authors: {active: true}).update_all(featured: true) # But for left joins or complex conditions, Rails may need to use subqueries # Be mindful of how these are translated to SQL for your specific database ``` Examine the SQL generated by your ORM and understand how database-specific optimizations are applied. This helps you write ActiveRecord queries that translate to efficient SQL for your database engine.