Question 1

What is a Large Language Model and how does it generate text?

Accepted Answer

**Target Audience:** Beginners to AI engineering — you can write code and call an API, but you have never looked inside a language model.
**Difficulty:** Easy
**Verified with:** Node 22.22.0 and Python 3.12.3 (the toy model in the example; no real model is called). Product and paper facts are cited inline with the date they were checked (October 2026).

> **How to read this doc:** Every idea is explained in plain language first, then tagged with `📌 Interview term:` so you also learn the exact w

Question 2

What are tokens and why do they matter for cost and limits?

Accepted Answer

**Target Audience:** Beginners who are about to ship (or pay for) their first LLM feature and keep seeing "tokens" on every pricing and limits page.
**Difficulty:** Easy
**Verified with:** Node 22.22.0 and Python 3.12.3 (a tiny BPE tokenizer and the cost arithmetic; no real tokenizer or model is called). Product facts and prices are cited inline with the date they were checked (October 2026).

> **How to read this doc:** Every idea is explained in plain language first, then tagged with `📌 Inter

Question 3

What is a context window and what happens when you exceed it?

Accepted Answer

**Target Audience:** Beginners building chat features, RAG or agents who have hit (or will hit) "context too long" errors.
**Difficulty:** Easy
**Verified with:** Node 22.22.0 and Python 3.12.3 (a simulated provider with a 200-token window; no real model is called). Provider behaviour is cited inline from documentation and forum reports, checked October 2026.

> **How to read this doc:** Every idea is explained in plain language first, then tagged with `📌 Interview term:` so you also learn the

Question 4

How do multimodal models handle images, audio and other non-text inputs?

Accepted Answer

**Target Audience:** Engineers who have used text-only LLM APIs and now need to send screenshots, scans, photos or audio.
**Difficulty:** Medium
**Verified with:** Node 22.22.0 and Python 3.12.3 (the patch-projection demo and the token estimators below; no real model is called). Provider token rules and paper details are cited inline with the source and the date checked (October 2026).

> **How to read this doc:** Every idea is explained in plain language first, then tagged with `📌 Interview te

Question 5

How does the transformer architecture and attention work?

Accepted Answer

**Target Audience:** Engineers who know what an LLM does from the outside and want to understand the inside well enough to explain it on a whiteboard.
**Difficulty:** Medium
**Verified with:** Node 22.22.0 and Python 3.12.3 (attention computed by hand on 4 tokens; no real model). Paper facts are cited inline, checked October 2026.

> **How to read this doc:** Every idea is explained in plain language first, then tagged with `📌 Interview term:` so you also learn the exact words an interviewer ex

AI ENGINEERINGDECODED.

Easy

What is a Large Language Model and how does it generate text?

What are tokens and why do they matter for cost and limits?

What is a context window and what happens when you exceed it?

Medium

How do multimodal models handle images, audio and other non-text inputs?

How does the transformer architecture and attention work?