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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 EngineeringIntermediate 8:02 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.
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
Before you start
This is the first lesson in the AI Models module, and it stands alone. It assumes three things:
A written deep dive at your own pace, with code that has been run before it was published.
03 · Practice
Alex's decision model labels a child seat as kids with 0.94 confidence, but their team files seats under parts. What does this show?
A short quiz that explains every answer, right or wrong.
See the whole lesson: Jev Explained: A Decision Model vs an LLM
§ 03
New lessons are added as they pass review.
8:02AI Engineering Intermediate 7 min read
An LLM writes an answer word by word. A decision model like Jev picks one answer from your list and says how sure it is, so software can act on every event. Here's how, and what's still unproven.
Oct 24, 2026
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
6:55System Design Intermediate 5 min read
A few lines of rough maths tell you how big a problem is before you design for it. Follow an exam results website from 21 requests a second to 1,500 at 8:00 am, and see what each number decides.
Oct 23, 2026
7:14System Design Beginner 6 min read
System design problems arrive vague on purpose. Follow a town planner through a bike-share scheme to learn five repeatable steps that stop you building the wrong thing well.
Oct 23, 2026
7:52System Design Beginner 6 min read
System design is choosing a system's parts and how they connect so it keeps its promises when many people use it at once. Learn it through one dumpling stall on a festival night.
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
§ 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.