- Backend Dev – Testing
Tests are how you change code you did not write without being afraid. What is worth testing and what is theatre, unit tests that run in milliseconds, integration tests against a real database, testing the API through HTTP, test data that does not rot, and why chasing a coverage number produces a suite that catches nothing.
- Breadth-First Search
Explore level by level using a queue — and get the shortest path in an unweighted graph for free, which no other traversal does. Reconstructing the path, why you mark visited on enqueue rather than dequeue, and where BFS stops being the right tool.
- Spring Boot – Cheat Sheet
The annotations and snippets from this whole track in one page, grouped by what you are trying to do — wire a bean, expose an endpoint, query a database, secure a route, cache a result, schedule a job. Written to be scanned rather than read, with a link to the lesson behind each one.
- iOS – Error Handling That Reaches the User
A typed error whose cases are the decisions a caller can make, not the places it went wrong. LocalizedError, field-level messages from a server, telling a cancelled request apart from a failed one, and the ViewState enum that makes the eternal spinner impossible to write.
- Python Advanced – Databases
Talking to a database from Python. The DB-API every driver implements, parameterised queries and the injection they prevent, transactions and context managers, connection pooling, and where an ORM earns its place.