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Go into your next system design interview, or your next design review, knowing why, not just what. Each lesson is an animated video, a written deep dive with code that runs, and a quick quiz, starting with AI Engineering and System Design.
AI EngineeringBeginner 7:12 video
§ 01
Each domain is split into modules, from fundamentals to the internals senior engineers know. Pick one and go deep.
Build real applications with LLMs, agents and tools.
Design systems that are fast, scalable and reliable.
Languages, frameworks and more, taught the same way.
§ 02
Every lesson gives you three ways into the same idea, because understanding sticks when you see it, read it and use it.
01 · Watch
A short animated explainer, narrated, with Vora as your guide: diagrams move, data flows, code runs.
02 · Read
What an eval method is
This is part 4 of the LLM Evals series, and it stands on its own. An eval method is the procedure that takes one output from your app and turns it into a verdict: pass or fail, a score, or a ranking. Criteria say what good means. The method is who or what decides.
A written deep dive at your own pace, with code that has been run before it was published.
03 · Practice
An assistant returns Sure! {"category": "delivery", "priority": "normal"} and the expected labels are delivery, normal. What should a programmatic check report?
A short quiz that explains every answer, right or wrong.
See the whole lesson: LLM Eval Methods: Code Checks, Human Review and LLM-as-Judge
§ 03
New lessons are added as they pass review.
7:12AI Engineering Beginner 6 min read
An eval method is the procedure that turns one output into a verdict. See code, a judge model and a person each judge the same five customer emails, and learn when each one is the right tool.
Oct 23, 2026
5:45AI Engineering Beginner 7 min read
Every LLM eval criterion answers one of three questions: is the answer any good, could it cause harm, and is it fast, cheap and reliable enough to run? Follow one support bot through each of them.
Oct 22, 2026
5:38AI Engineering Beginner 6 min read
A RAG chatbot can fail in its retriever, its generator, the flow between them or the app as a whole. Follow one customer's question to see why checking only the final answer can't tell you which part broke.
Oct 22, 2026
6:28AI Engineering Beginner 4 min read
LLM evals are systematic, repeatable tests that judge an LLM app against clear criteria. Learn why spot checks fail, how evals differ from classic tests, and the workflow to run them.
Oct 19, 2026
§ 04
Engineers preparing for AI Engineering and System Design interviews, and engineers building real systems who want to know why things work, not just what to type. Both get the same thing: one topic, understood properly.
Yes. Every lesson, video and quiz is free. No paywalls, no pop-ups.
No, there's no sign-up. When you mark a lesson as done, that's saved in your browser only, so it stays on this device and nothing is sent to us.
An animated, narrated video with captions, a written deep dive with callouts and key takeaways, code that is run in a sandbox before it's published, and a short quiz.
Each lesson starts from the author's own notes. Every claim is checked, every code example is run in a sandbox, and the author reviews and signs off on each lesson before it goes live.
There's no fixed schedule: new lessons are added as they pass review. The RSS feed, linked in the footer, announces each one.
Email support@codestoa.com if something isn't working, like a video that won't play or a broken link. Email feedback@codestoa.com to report a mistake in a lesson or suggest a topic. The author reads every message.