Free reference
Interview Brush‑Up
Learn a concept, understand it properly, or brush up the night before an interview. Topic by topic, concept by concept. Free.
Short on time? Every concept starts with the one-line version, and the summary is up top.
Want depth? Keep scrolling: diagrams, real code, trade-offs and edge cases.
AI
AI Concepts
LLMs from the point of view of the engineer who has to ship them: workflows, agents, cost, testing.
- Prompt chaining
System Design Concepts
The building blocks behind every design round, and how they are really built.
- Timeouts
- Retries
- Idempotency
- Stateless vs stateful
- Concurrency vs parallelism
- Reliability vs availability
- Deployment strategies
- Cache busting
- When an index gets ignored
Walk-throughs of a whole scenario, like seat booking on release day, live in Articles.