Essential Developer (essentialdeveloper.com) is a UK-based iOS / Swift training company run by Mike Apostolakis and Caio Zullo, focused on the senior-engineering side of iOS work — TDD, Clean Architecture, modular code design, and the production patterns that scale iOS codebases past the small-app size.
The CourseFlix listing carries two Essential Developer courses: iOS Dev Mentoring Sessions and iOS Dev Tooling. The teaching style is unusually rigorous for the iOS-tutorial market — material is taught at the level of architects responsible for codebases that will run in production for years.
Material is paid and aimed at intermediate-and-up iOS developers ready to take TDD and software-architecture work as serious professional disciplines. For broader content, see CourseFlix's Swift category page.
