Andrew Atkinson is a US software engineer focused on the production-engineering side of PostgreSQL, particularly when paired with Ruby on Rails. He is the author of High Performance PostgreSQL for Rails (Pragmatic Bookshelf), a comprehensive treatment of the database-side concerns that show up when Rails applications scale.
His CourseFlix listing carries High Performance PostgreSQL for Rails — covering query optimisation, indexing strategy, the Rails-specific N+1 patterns, replication, and the operational disciplines that keep large Rails-and-Postgres applications fast.
Material is paid and aimed at Rails engineers responsible for database performance on real production systems. For broader content, see CourseFlix's Ruby on Rails category page.