Why-How

Short essays on famous ideas in technology and science. Each one starts with why it exists — the problem it solves — and only then explains how it works.

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Hardening a cloud server Spin up a fresh VPS, wait an hour, and the auth log already has thousands of brute-force attempts from across the internet. Every server-hardening guide says roughly the same things — here's what each one actually stops, and where the rules are theater. Security · May 25, 2026
How end-to-end encryption works Open WhatsApp and a banner tells you Meta can't read your messages. That claim sits on a specific protocol — Diffie–Hellman key agreement plus a 'double ratchet' that changes the key on every message. Here's the shape of it. Security · May 24, 2026
How does an LLM 'see' an image? You paste a screenshot into ChatGPT and it reads the text, describes the scene, answers questions. But the model only ever predicts text tokens — so how does a picture get into it at all? AI & ML · May 20, 2026
What are 'weights' in an LLM? When Meta releases 'open weights' for Llama, what's actually in that file? A giant table of numbers and nothing else — so how does a pile of numbers know things? AI & ML · May 16, 2026
Why compression works at all Zip a photo and it shrinks; zip the zip and it doesn't. Compression isn't magic — it only ever exploits the patterns that were already there. Computer Science · May 14, 2026
Why CPUs have three levels of cache Look at a CPU die shot and you'll find more area spent on memory than on math — and that memory is split into L1, L2, and L3. The split exists because no single cache can be both big and fast, so the chip builds a ladder instead. Science · May 14, 2026
Why deadlocks need four conditions A deadlock feels like bad luck, but it can only happen when four specific conditions all hold at once — and breaking any one makes it impossible. Systems · May 14, 2026
Why garbage collectors pause your program A tracing collector can't safely move or free an object while your code is mid-read — so it freezes the program to get a consistent snapshot, and generational collection is one common trick for keeping the freeze short. Systems · May 14, 2026
What is tool use (a.k.a. function calling)? A model that only emits text somehow ends up booking your flight. The trick isn't in the weights — it's in the contract between model, harness, and your code. AI & ML · May 7, 2026
What does 'X parameters' mean in an LLM? Llama 3.1 70B, DeepSeek-V3 671B, Phi-4 14B — what is that number actually counting, and why is it the headline figure on every model release? AI & ML · May 4, 2026