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Build Firebase AI Logic with Antigravity CLI Note: Google Cloud credits are provided for this project. In this blog post, I demonstrate how to use the Antigravity CLI (an agentic AI assistant integrating directly with development workflows via skills and servers) to build an image analysis demo using Angular, the Firebase Hybrid & On-device Inference Web SDK, and Gemini models. Users upload an image and use a Gemini model to analyze it to generate a few alternative texts, tags, recommendations, and CSS tips to enhance the image quality. When the demo is running in Chrome 148+, the Hybrid & On-device SDK leverages the Prompt API of the on-device Gemini Nano model to perform the image-to-text tasks, and the token usage is 0. When other browsers, such as Safari or Firefox, execute the same tasks, the SDK falls back to Cloud AI (Gemini 3.5 Flash model), which consumes tokens. Next, I describe how to install the skills in my Angular project and register the Angular and Stitch MCP servers in the Antigravity CLI to develop the infrastructure, services, and UI design of my demo. 1. Workflow This is my entire workflow from implementing features, generating UI screens, and mapping the screens to Angular components. 2. Skills I installed the grill-with-docs , angular , and firebase skills in my project for the following reasons: grill-with-docs: Conduct a rigid Q&A session to generate a specification for a feature, refactor, or critical fix. AI is responsible for performing thorough analysis, and putting in more efforts to generate code to achieve the task. domain-modeling: The skill is referenced in the SKILL.md of the grill-with-docs skill, so a copy of it is required. code-review: Spawn two sub-agents to review changes to detect code smells and verify that the changes align with the specification. angular: Provide the best practices of modern Angular architecture, such as using signals and signal forms. firebase: Provide the skills for Firebase AI Logic, Firebase Remote, et

Twelve pricing tabs open. Neon, Hetzner, Supabase, Prisma, Scaleway, OVH. My database is half a gigabyte. I was comparing ten-terabyte price curves. At some point this week I typed the words "I am super lost here" about my own infrastructure. I advise companies on this exact class of decision. That sentence still came out of my hands. If you have ever spent an evening deep in provider pricing pages for a workload that fits on a USB stick from 2009, this one is for you. All numbers below come from the live pricing pages as of July 2026. Rates move, so verify before you commit. Three fears, all pointed at the wrong layers I went in worried about getting attacked, running out of space, and being locked in. All three dissolved under ten minutes of honest reading. DDoS lands on the website edge, not the database. My site already sits behind Cloudflare and Vercel, and a database is never publicly exposed. Only the app talks to it. Whichever provider I picked, that attack surface stayed identical. Here is the shape of the stack, and where each fear lives. MANAGED (what I run today) visitors ──> Cloudflare edge ──> Vercel app ──> managed Postgres [DDoS absorbed] [stateless] [never public, app-only access, provider patches, provider backups, provider on-call] SELF-HOSTED (the alternative I priced) visitors ──> Cloudflare edge ──> Vercel app ──> Hetzner CAX11 [DDoS absorbed] [stateless] [Postgres :5432 firewalled to app, SSH hardened, fail2ban + auto- patching = MINE] │ pg_dump every 6h ▼ encrypted ────> Cloudflare R2 [off-site copies] Same edge, same app, same attack surface. Everything in the right-hand box is what changes owners. Storage was a rounding error. My data is 0.5 GB. Even the cheapest self-hosted box includes 40 GB, eighty times headroom before the first extra cent. Lock-in was a phantom too. Managed Postgres is still stock Postgres. Exiting means a dump, a restore, and one connection string change in the deployment environment. Minutes of cutover, no rewrite an

The first sign something was wrong wasn't a crash. It was a pattern. blockly-platform was the first real thing I built with Claude Code end to end — a Blockly-based platform for university programming exercises, driven entirely through Claude Code's Telegram channel. No editor open, no repo checked out on my machine, just a chat thread. I'd describe what I wanted, Claude Code would build it on a box I never looked at directly, and I'd judge the result by clicking around the deployed app. On March 22nd, the home page came up empty. GET /api/exercises/published was returning 403. I said so in the chat; a few messages later, Claude Code said it was fixed — the endpoint hadn't been added to Spring Security's permitAll() list. I moved on, tried the category filter. Also empty, also 403, also missing from the same permitAll() list — same file, same class of fix, different line. Then the exercise detail page. Same story, third time, same day. Three days later, the like button stopped working — root cause, again: POST /api/exercises/*/like had never been whitelisted either. Four times, one file, one recurring gap. None of these were hard bugs. Each one, in isolation, is a one-line fix a competent engineer makes without thinking twice. What bothered me, once I noticed the pattern, was that I hadn't noticed it as it happened. I had no diff to scroll through, no file to glance at and think "wait, didn't we just fix this exact class of thing twice already?" I had a chat log and a live app to poke at. The fourth fix looked, from where I sat, exactly like the first: a message telling me it was resolved. That was the moment I started to suspect the problem wasn't the model. It was that nobody — not the model, not me — had anything to look at. Why chat-only vibe coding breaks down Here's what makes that pattern more interesting than "the AI made a mistake": every one of those four fixes was correct. Claude Code read the error, found the missing permitAll() entry, added it, and move

In an AI-powered reporting project, the backend API response time suddenly jumped to 8 seconds; I couldn't find a solution by examining only the frontend code to isolate the issue. This experience highlighted how the lack of a full-stack developer, who can see API, data layer, and model integration simultaneously, can slow down a project. Below, I will analyze step-by-step whether being full-stack is truly necessary in the age of AI. Why is Being Full-Stack Necessary in the Age of AI? The primary benefit of being full-stack is enabling a single developer to have end-to-end control of AI systems. This is because training a model, saving it to a vector database, and serving it via a REST API all occur at different layers; each of these layers might require a separate area of expertise. However, a full-stack developer, by being able to see the entire process from the data collection script ( python collect_data.py ) to the model service ( uvicorn app:app --host 0.0.0.0 ), can catch integration errors faster. Let's illustrate this advantage with a concrete example: within a project, I automated model retraining using a systemd timer and saw “Active: active (waiting)” in the systemctl status model-retrain.timer output; however, the API layer's GET /predict response was still returning the old model. Identifying the issue was only possible by simultaneously examining the timer configuration and the API code; without switching between separate teams. Summary: Full-stack proficiency provides the ability to detect and resolve potential incompatibilities within the complex data-model-service chain of AI projects at a single point. How Do Full-Stack Skills Contribute to AI Projects? A full-stack developer keeps all steps, from data preprocessing ( pandas script) to the model service ( FastAPI endpoint), within a single codebase. This simplifies version control and the CI/CD workflow. For example, when I define a postgres service, a redis cache, and an api service within docker

Cet article a été publié à l'origine sur WP Admin Lab , le journal du web technique en français. WP-CLI est l'interface en ligne de commande officielle de WordPress, un outil indispensable pour tout développeur ou administrateur gérant des sites WordPress en production. Contrairement à l'interface graphique du tableau de bord, WP-CLI permet d'exécuter des opérations en masse, d'automatiser des tâches répétitives et d'intervenir sur des sites inaccessibles via le navigateur. En 2026, maîtriser WP-CLI est devenu une compétence fondamentale pour la gestion professionnelle de parcs WordPress, que ce soit pour des agences gérant des dizaines de sites ou pour des développeurs travaillant sur des environnements de staging et de production. Installation et configuration de WP-CLI en 2026 L'installation de WP-CLI s'effectue en téléchargeant le fichier Phar officiel depuis le dépôt GitHub du projet et en le rendant exécutable à l'échelle du système. Sur les serveurs Linux mutualisés ou dédiés, la commande curl -O permet de récupérer le binaire, que l'on déplace ensuite vers /usr/local/bin/wp avec les droits d'exécution appropriés. Les hébergeurs comme Kinsta ou WP Engine proposent WP-CLI préinstallé dans leurs environnements SSH, facilitant la prise en main immédiate. La vérification de l'installation avec wp -info fournit les détails de version, l'interpréteur PHP utilisé et le chemin vers le fichier de configuration wp-config.php. La configuration avancée de WP-CLI passe par le fichier wp-cli.yml placé à la racine du projet WordPress. Ce fichier YAML permet de définir l'URL du site, le chemin d'installation, les alias de serveurs distants pour les déploiements SSH, et des paramètres par défaut pour certaines commandes. Les alias SSH dans wp-cli.yml sont particulièrement puissants : ils permettent d'exécuter des commandes WP-CLI sur un serveur distant exactement comme en local, avec une syntaxe du type wp @production plugin list. Cette fonctionnalité simplifie considérableme

AI-assisted builders can take an idea from prompt to production in a weekend. That speed is useful, but it also compresses the part of the process where someone normally reviews deployment settings, browser-visible secrets, authorization boundaries, and recovery plans. A public security scanner is a good first pass for that problem. It is also easy to misunderstand. A clean public scan does not mean an application is secure, and a warning does not always mean a vulnerability is exploitable. The useful question is not “Did the scanner pass my app?” It is “What evidence could this scanner actually observe?” Layer 1: the public deployment surface A passive scanner can request the same resources that a normal visitor can reach. Depending on its scope, it may inspect: HTTP security headers such as Content-Security-Policy and Strict-Transport-Security HTTPS behavior and redirect consistency Public JavaScript bundles for credential-shaped strings Public source maps that expose original source structure Common sensitive paths such as environment files or repository metadata Cookie attributes and other response-level deployment signals These checks are valuable because they test the deployed result, not the configuration you intended to ship. For example, a repository may contain a CSP configuration while the CDN response does not. A source map may be disabled in one build configuration but still appear in production. A key may be stored safely on the server in most code paths while one client bundle accidentally contains a privileged token. The deployed surface is where those mistakes become observable. Layer 2: source-code review A public URL cannot reveal every control behind an application. Source review or SAST can inspect code paths, configuration, data flow, and dangerous implementation patterns that never appear in a normal response. This is where you can answer questions such as: Is authorization enforced on the server? Can a user change an object ID and read anothe

Sanity vs Directus is a comparison that comes up more than you'd expect on technical forums in 2026, usually from teams who already have a Postgres database running and are wondering why they'd pay for a separate content lake when Directus can wrap what they have. It's a fair question. These two tools solve adjacent problems but from genuinely different starting points, and the right choice depends heavily on whether your content is primarily relational data or editorial content. What each tool actually is Sanity is a hosted content platform. Your content lives in Sanity's managed "content lake" — a document store with real-time collaboration, a CDN-backed asset pipeline, and GROQ as the query language. You define schemas in code, deploy a customisable Studio, and talk to Sanity's API from your Next.js app. You do not manage infrastructure. Directus is an open-source data platform that wraps any existing SQL database — Postgres, MySQL, SQLite, MS SQL — and exposes it through a REST API, a GraphQL endpoint, and a web-based admin UI. Schema changes happen in the admin UI (or via migrations), and your data stays in your own database. You can self-host entirely or use Directus Cloud. That distinction — hosted content lake vs database-wrapper — drives nearly every practical difference between them. Data ownership and where your content lives With Sanity, your content lives in Sanity's infrastructure. You can export it via the export API, but you are operationally dependent on Sanity's uptime and their CDN. For most product teams that's fine — Sanity has been reliable and their SLA on Growth/Enterprise tiers is solid. But if you're in a regulated industry, have strict data residency requirements, or your client contract requires them to own the database, it's a real constraint. With Directus, the database is yours from day one. You point Directus at a Postgres instance on your own infrastructure (or a managed one like Supabase, Neon, or Railway), and Directus adds the API

Building a Lightweight Product Filter with Vanilla JavaScript While building a small e-commerce project, I wanted users to filter products instantly without refreshing the page. Instead of relying on a frontend framework, I opted for a simple solution using HTML data attributes, vanilla JavaScript, and a little CSS. The goal was straightforward: let visitors filter items by size while keeping the interface fast, responsive, and easy to maintain. HTML Structure Each product card stores its information in data-* attributes. This keeps the markup clean and makes filtering straightforward. <div class= "filters" > <button class= "filter-btn" data-filter= "all" > All </button> <button class= "filter-btn" data-filter= "small" > S </button> <button class= "filter-btn" data-filter= "medium" > M </button> <button class= "filter-btn" data-filter= "large" > L </button> </div> <div class= "product-grid" > <div class= "product-card" data-size= "medium" data-style= "cargo" > Cargo Shorts </div> <div class= "product-card" data-size= "large" data-style= "chino" > Chino Shorts </div> <!-- More product cards --> </div> Using data attributes means you can add new filter categories later without changing your overall structure. JavaScript Filtering Logic The filtering logic listens for button clicks and simply shows or hides product cards based on the selected size. const filterButtons = document . querySelectorAll ( " .filter-btn " ); const productCards = document . querySelectorAll ( " .product-card " ); filterButtons . forEach (( button ) => { button . addEventListener ( " click " , () => { const filterValue = button . dataset . filter ; productCards . forEach (( card ) => { const cardSize = card . dataset . size ; if ( filterValue === " all " || cardSize === filterValue ) { card . classList . remove ( " hidden " ); } else { card . classList . add ( " hidden " ); } }); filterButtons . forEach (( btn ) => btn . classList . remove ( " active " )); button . classList . add ( " active "

Hi guys ! I'm a new developer who's interested in data science and artificial intelligence. To showcase what I learnt thus far, I've started writing articles, with my first one being published here ! One of the most difficult parts of getting into machine learning was the overload of terminology that tutorials had, even when explaining basic concepts such as how a neural network itself would function. Because of this, I've written an article (see above) that simplifies it while ensuring the main concepts are sufficiently explained; it requires no mathematical background and will only take less than 5 minutes to read ! I hope you find it informative and well written, and I highly welcome any suggestions or corrections that might be suggested to improve my future articles !

AI schedules your whole week to take action Discussion | Link

A markdown editor you and your agent co-edit Discussion | Link

Hoi hoi! I’m @nyaomaru, a frontend engineer currently fighting the intense European heatwave by...

Knowledge-and-Memory-Management v0.0.2 is out, delivering a clean release that prioritizes portability and modularity. This version shifts from hardcoded personal paths to $AGENT_HOME , making your knowledge pipelines reproducible across environments. If you’re building autonomous systems that need to ingest web content, video transcripts, or articles, this is the update you’ve been waiting for. The core design separates collection from memory management. The knowledge_collector module handles ingestion, while memory_manager handles storage, retrieval, and decay. The $AGENT_HOME environment variable anchors all runtime paths—no more hardcoded /home/user strings. Set it once, and your agents can carry their knowledge base anywhere. Knowledge Collection: Web, Video, Articles The collector supports three primary sources: Web : Scrapes and parses HTML, extracting body text and metadata. Handles rate limiting and retry logic. Video : Takes a YouTube URL, downloads captions (if available) or generates transcripts via Whisper integration. Articles : Parses RSS feeds or direct PDF links, chunking content by sections. All sources normalize into a KnowledgeEntry dict: {source, timestamp, content, embeddings} . The collector writes raw entries to $AGENT_HOME/knowledge/raw/ and passes them to the memory manager for processing. Memory Management with $AGENT_HOME The memory manager is where the clean release shines. Previous versions used os.path.expanduser("~/knowledge") , which broke across systems. v0.0.2 requires $AGENT_HOME to be set, then constructs all paths relative to it: $AGENT_HOME/memory/ stores persistent memories. $AGENT_HOME/knowledge/ holds raw and processed collections. $AGENT_HOME/config/ contains source definitions and memory decay rules. This design lets you ship a single agent.env file with AGENT_HOME=/opt/myagent or %AGENT_HOME%\data —no platform-specific configuration. The memory manager indexes entries by semantic embeddings (via a pluggable model provider

The dashboard says forty instances, up from twelve this morning. The autoscaler did its job: it saw latency climb and threw hardware at it. And latency got worse. Not flat. Worse. You're paying for three times the compute to serve a slower product. Somewhere under all forty of those boxes is a single thing they're all waiting in line for, and every instance you add makes the line longer. Horizontal scaling multiplies work that doesn't have to coordinate. The instant the work does have to coordinate, more instances make it slower. Amdahl wrote this down in 1967: the serial fraction of a job sets a hard ceiling on how much faster you can go, no matter how much hardware you throw at the parallel part. Neil Gunther's Universal Scalability Law goes further: past a certain point, the cost of nodes coordinating with each other bends the curve back down. Add capacity, get less throughput. That ceiling was not set by the autoscaler, and it will not be moved by the autoscaler. It was set a long time before this morning, in a room, by whoever decided where the state lives and who has to touch it at the same instant. Now hand the service to a fleet of agents. It writes you something that looks built to scale: stateless handlers, a tidy repo, green tests, a canary that bakes fine at 1% traffic. Every gate you trust says ship it. And the bottleneck is sitting right there in the design, invisible to all of it, because the mistake isn't in the lines, it's in the shape. You cannot catch a shape problem by reading a diff. Name the hot state before you pick a framework. Where does the contended state live, and which requests touch it at the same instant? Answer that out loud, before anyone opens an editor. The tool is downstream of that answer, every time. Originally published at https://imacto.com/writing/scale-is-a-design-not-a-dial . Written with Claude Opus 4.8.

i've been that person. standing in front of leadership with an 18-month architecture diagram, explaining why we need six months of infrastructure before a user touches a single feature. and it made sense. for 25 years it made sense. writing boilerplate was expensive. every feature came with a tax — database migrations, routing config, auth wiring. build a shared platform first, pay that tax once. the roadmap justified the investment. then i saw a stat that wouldn't leave me alone. roughly 60% of features on a six-month roadmap are obsolete by launch. not slightly off. obsolete. the customer's problem shifted. the market moved. you spent six months building a precise answer to a question nobody asks anymore. the longer you invest before showing something real, the more expensive it is to admit you were wrong. so you don't. you ship the wrong thing and call it "on schedule." i've done it. i've watched it happen. AI didn't create this problem. but agents are making it impossible to ignore. the 82-point gap mckinsey's 2025 survey: 88% of organizations use AI. only 6% see real bottom-line impact. that 82-point gap isn't about tools. everyone has the same tools. but something shifted in their may 2026 report. they describe agents working overnight — enriching requirements, generating code, packaging outputs for morning review. they call it the "24-hour sprint." leading organizations see 3-5x productivity with 60% smaller teams. a product owner logs in at 9am and finds a feature went from requirements to tested code overnight. nobody worked late. agents did. that's not autocomplete. that's a different delivery model. and here's what most teams miss: it only works when the work is small, bounded, and complete. agents need to know where a task starts and ends. horizontal platform architectures don't give them that. the codebase is the prompt jeremy d. miller built wolverine for .NET. in june 2026 he wrote: "the structure of your codebase is now, effectively, part of the prom

You installed TypeScript 7, ran your build, and something broke. Maybe ESLint crashed with a cryptic TypeError: Cannot read properties of undefined (reading 'Cjs') . Maybe ts-jest stopped transforming your test files. Maybe your CI pipeline just went red for no reason you can point to. You're not doing anything wrong. TypeScript 7 shipped tsgo, a genuine Go port of the type-checker, not a rewrite from scratch. But the tools that plug into TypeScript don't talk to the type-checker directly, they talk to a programmatic API. That API isn't stable yet, it lands in 7.1. Until then, a chunk of the ecosystem throws errors the moment you point typescript at the new version. The 10-second version Don't replace typescript in your dependencies with the 7.x line if you use typescript-eslint, ts-jest, ts-morph, or any tool doing programmatic type-checking. Keep typescript pinned to 6.x for those tools, and install @typescript/native-preview alongside it purely for fast type-checking in CI or a manual tsgo --noEmit command. Two compilers, living side by side, each doing a different job. Why this is happening The TypeScript team calls this Project Corsa: a line-by-line port of the compiler from the old JavaScript codebase (Strada) into Go (Corsa), preserving identical type-checking behavior while getting roughly 10x faster builds from real OS threads instead of Node's single-threaded event loop. That preservation is impressive, but it's a port, not a reimplementation with a new API surface. Tools like typescript-eslint depend on the programmatic API to walk your AST and pull type information out of the compiler, and that API isn't ready until 7.1. What's actually broken right now typescript-eslint — npm refuses to install alongside typescript@7 at all (ERESOLVE error), because the published peer range only allows versions below 6.1.0. Force it through and ESLint crashes deep inside typescript-estree . Tracked as typescript-eslint issue #12518, closed as not planned since the real

i've been the incident commander who forgot to write down the first 20 minutes of the timeline because i was too busy reading logs. more than once. the war room is chaos — five engineers pasting logs, someone asking if the deploy from 30 minutes ago is related, nobody documenting anything. you start logging events in a doc while reading error logs while drafting a stakeholder update while deciding whether to rollback. you're the bottleneck. not because you're bad at your job — because you're doing four jobs at once. i got tired of watching smart people spend their incident energy on documentation instead of decisions. so i built ai-incident-commander — a CLI tool that handles the mechanical parts. timeline, updates, remediation research, postmortem draft. you make the calls. it does the paperwork. runs on your laptop with a local LLM. no API keys, no cloud, no docker. github.com/deghosal-2026/ai-incident-commander — MIT licensed. what it does one command: pip install git+https://github.com/deghosal-2026/ai-incident-commander.git incident-commander simulate --scenario db-connection-pool --auto-approve 8 pre-built scenarios ship with it. database connection pool, bad deploy, memory leak, cert expiry — the usual suspects. no real data needed to try it. for actual incidents, you point it at a directory with your alert, logs, messages, and github PRs. it outputs 10 markdown files: timeline, stakeholder updates, comms blocks you can paste straight into slack, remediation suggestions, a blameless postmortem, and a cost report. the safety part was the real engineering. three points in the pipeline where the graph pauses and waits for you to say yes — stakeholder update, remediation, postmortem. the AI never ships anything without approval. every remediation comes with a citation. suggestions below 0.7 confidence get suppressed. the postmortem prompt enforces blameless language. all AI content gets labeled [AI-GENERATED — review carefully] . and it never executes anything. i

Last month I finally did some math I'd been putting off: how much I was actually paying to keep a bunch of sites online. $39/month on Hostinger (about R$200, I'm in Brazil). For hosting 10+ sites: product landing pages, blogs, a couple of small tools. Every month, on autopilot, straight off the card. Then I asked myself the obvious question I'd been avoiding: out of those 10+ sites, how many actually need a server running 24/7? Answer: none. What these sites actually are A product landing page doesn't need PHP processing a request. A blog doesn't need a database query on every page view. A marketing site doesn't change its content every second. That's HTML, CSS, and JS you can generate once and serve from a CDN. In other words: a static site. A few real examples I migrated: eduardovillao.me → my personal blog, built with Astro formroute.dev → a SaaS landing page, plain HTML wpfeatureloop.com → a dev tool landing page, plain HTML Three different kinds of sites (blog, SaaS, dev tool), two different stacks, and none of them needed a server running around the clock just to exist. The reason I hadn't migrated sooner wasn't technical. It was inertia. "It's already paid for, it already works, leave it alone." Classic. The migration I moved everything to Cloudflare Pages . The reasoning is boring because it's so simple: it's free, global CDN, automatic SSL, Git-based deploys, custom domains at no extra cost. For static sites, there's really nothing to debate. The process, in short: Each site became a repo (or a folder inside a monorepo, depending on the case) Connected the repo to Cloudflare Pages Set up the build, mostly plain HTML, Astro for the blog where I wanted content collections and a proper writing workflow Pointed the domain, SSL came up on its own Cancelled hosting for that domain on Hostinger Repeated that site by site. No magic, just repetitive work, but each one took about 20-30 minutes. (If you want the technical deep dive on one specific migration, including

If you have an interview in the next few hours and need to quickly revise Abstraction in C++ , this guide is for you. No long theory. No unnecessary examples. Only the concepts interviewers expect you to know. 📌 What is Abstraction? Definition Abstraction is the process of exposing only the essential behavior of an object while hiding unnecessary implementation details. Remember WHAT ↓ Hide HOW The user knows what an object can do, but not how it performs the work. ❓ Why Do We Need Abstraction? Without abstraction: Every developer needs to understand internal implementation. Client code becomes tightly coupled. Maintenance becomes difficult. With abstraction: Developers interact with a simple interface. Internal implementation can change without affecting users. Systems become easier to extend and maintain. Benefits ✅ Reduces complexity ✅ Promotes loose coupling ✅ Improves maintainability ✅ Supports extensibility ✅ Enables cleaner architecture ⚙️ How Does C++ Achieve Abstraction? C++ primarily achieves abstraction using: Abstract Class + Pure Virtual Functions + Runtime Polymorphism 🏗️ What is an Abstract Class? An abstract class is a class that contains at least one pure virtual function . It represents a: ✅ Contract ✅ Blueprint ✅ Common capability Because it is incomplete , it cannot be instantiated . 🎯 What is a Pure Virtual Function? Syntax virtual ReturnType functionName () = 0 ; Meaning It tells the compiler: Every concrete derived class must implement this function. = 0 does NOT mean "return zero." It simply marks the function as pure virtual . 🧠 Mental Model Think of it like this: Job Description ↓ Employee The job description defines responsibilities. Each employee fulfills those responsibilities differently. Or: Blueprint ↓ House You don't live inside a blueprint. You build a house from it. Similarly, you don't create objects of an abstract class—you create objects of concrete derived classes. 🏭 Practical Software Example Imagine an e-commerce application

LIA is a hyperlocal employability platform I'm building for an isolated coastal district in Brazil — think fixed retail jobs, gigs, and a reputation layer, all matched by proximity instead of routed through a national job board. This post is about the implementation: the actual folder structure, the real RegisterUserUseCase, and the Argon2id decision — pulled straight from the repository, not reconstructed from memory. The Clean Architecture folder structure LIA's backend is organized in four layers, and the direction of dependency is non-negotiable: outer layers depend on inner layers, never the other way around. backend/src/ ├── domain/ │ ├── entities/ │ └── repositories/ # interfaces only ├── application/ │ ├── dto/ │ └── use-cases/ ├── infrastructure/ │ ├── database/ │ └── repositories/ # Prisma implementations ├── presentation/ │ ├── controllers/ │ └── routes/ └── shared/ └── errors/ Let's walk through the registration feature end to end, following that exact order. Domain — the entity and the repository contract The User entity is a plain interface. No decorators, no ORM annotations, no framework leaking in: typescript// domain/entities/user.ts export interface User { id: string; name: string; email: string; password: string; createdAt: Date; updatedAt: Date; } The repository is defined as a contract, not an implementation. The domain doesn't know — and doesn't care — whether it's backed by PostgreSQL, an in-memory map, or something else entirely: typescript// domain/repositories/user.repository.ts import { RegisterUserDTO } from '../../application/dto/register-user.dto.js'; export interface UserRepository { create(data: RegisterUserDTO): Promise<{ id: string; name: string; email: string; createdAt: Date; updatedAt: Date; }>; findByEmail(email: string): Promise<{ id: string; name: string; email: string; password: string; createdAt: Date; updatedAt: Date; } | null>; } Notice create() never returns the password hash. That's not an accident — it's the same "strip