freeCodeCamp

Bloom Filters Explained: The Probabilistic Data Structure Powering Instagram, Google, and High-Scale Systems

Oluwaseyi Fatunmole |
Instagram has over 500 million registered usernames. When a new user tries to register, the platform needs to answer one question almost instantly: has this username already been taken? The naïve answ... read more

How Firestore Structures Data and How to Perform CRUD Operations With It

Caleb Mintoumba |
Most apps eventually need to store and manipulate data. And if you're building with Firebase, that data lives in Firestore, Google's flexible, scalable NoSQL document database. But before you can conf... read more

What Every Dev Should Know About Tracking Product Data

Obum |
Product data is the record of what actually happens inside your app or website. It shows what your users do, how your system behaves, and how your business performs. In this article, you'll learn what... read more

Learn the AI SDLC – The Complete Guide to Building Agent Skills

Sarvesh Talele |
Perhaps you can relate to this scenario: you've explained AI models four times using the same instructions this week. You've talked repeatedly about how your team structures a deck. Which checks run b... read more

How to Build Characterization Tests Before Refactoring Legacy Code

Hugo Teijiz |
The first thing many engineers want to do when they inherit legacy code is improve it. You find a function that's difficult to understand. Or you see duplicated logic, deeply nested conditions, databa... read more

How to Build API Documentation From Scratch [A Roadmap for Technical Writers]

Gloria Tejuosho |
As a technical writer, building public-facing API documentation from scratch for a real product can feel like a dream come true, especially if you’ve only been documenting fictional APIs or updating e... read more

How to Automate Your Tests in Express Using Vitest

jabo Landry |
Thinking through API logic while constantly switching tabs to test application integration can be overwhelming and time-consuming. Well, you can save your time and energy by writing tests for your app... read more

From Mixtral to Kimi K3: How Mixture-of-Experts Models Evolved

Botao Deng |
In this article, we'll discuss how Mixture-of-Experts models grew from a handful of experts to nearly 900 per layer, and the compression and stability mechanisms that keep such a sparse design trainab... read more

I Added a CDN Cache to My Site and It Got Slower. Here's the Math I Should Have Done First.

Javeed Shaik |
Last week I put a CDN cache in front of a static site, expecting it to get faster. But instead, it got measurably slower. Not subtly: an independent crawler that had flagged 38 slow pages before the c... read more

How to Get Reliable Structured Data Out of an LLM

Vineeth Pawar |
Most tutorials about calling a language model end at JSON.parse(response.content). That line works on your first ten test cases. Then you ship, and somewhere around request four hundred the model retu... read more