- Spring Boot – Sending Email
JavaMailSender, a MimeMessageHelper for HTML and attachments, and rendering the body from the Thymeleaf template built earlier in the track. Sending it off the request thread, and testing the whole thing against a local sink instead of a real inbox.
- iOS – Building a Design System
Tokens, a semantic layer over them, and components that consume the semantic layer — the three tiers, and why skipping the middle one makes a retune impossible. ViewModifier versus wrapper view, ButtonStyle instead of a custom button, and writing a Layout by hand when SwiftUI ships nothing that wraps.
- Python Advanced – Serialization
Turning objects into bytes and back. Custom JSON encoders for the types json refuses, why pickle is a remote code execution risk rather than a file format, YAML's safe_load rule, and round-tripping dataclasses without writing the mapping by hand.
- Python – Modules & Packages
Splitting code across files. What import really does, the search path, packages and `__init__.py`, the `if __name__ == "__main__"` guard, and why a circular import is a design problem rather than a syntax one.
- Frontend Dev – What to Learn in a Framework
The small part of a big framework you use every day. Components and props, the render model, effects and when you do not need one, composition over configuration, and the project-level concerns every framework makes you answer — structure, dependencies, and per-environment configuration. React here, but the checklist is portable.