- Backend Dev – Databases
The part of the job that bites hardest and gets taught least. Modelling a schema you can live with, the indexes that decide whether a query takes 2ms or 2 seconds, what a transaction guarantees and what it does not, ORM versus plain SQL and when to drop down, the N+1 problem, connection pools, and migrations you can run on a live table.
- Priority Queues
A queue that serves by priority rather than by arrival. What Java's PriorityQueue is underneath, the comparator that decides min-heap or max-heap, the k-largest pattern that beats sorting, and the iteration order that is not sorted and surprises everyone.
- 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.