Blog

Articles on programming, AI agents, online business and entrepreneurial mindset. All from the trenches, building real products.

You're Pushing the System in the Wrong Direction (And That's Why Nothing Changes)

Most people work hard to change their results by tweaking the wrong parameters. Donella Meadows discovered this decades ago: the highest leverage points in any system are never the obvious ones. This article teaches you how to read the feedback loops in your life and push in the right direction.

·1 min read
Programming

Prompts That Actually Work in Claude Code (And the Mistake 90% of Devs Make)

Weeks using Claude Code with mediocre results. Then I changed one thing about how I prompted it and the difference was massive. It's not the model. It's you talking to it like it's a search engine.

·1 min read

Scarcity Mindset Is the Biggest Risk You're Taking (And You Don't Even Know It)

The people I know who 'guard their secrets' are in the exact same place they were three years ago. The ones who share everything keep moving forward. It's not a coincidence: scarcity mindset doesn't protect you, it paralyzes you. Here's why shifting that mental model is the most important strategic decision you can make in 2026.

·1 min read
Projects

The Impossible Marketing Problem of Nautilus VPN: How Do You Sell Privacy Without Betraying It?

Selling a VPN has a brutal contradiction at its core: almost every marketing tool you'd use to grow violates exactly what you're promising your user. Here's how I solved it in Nautilus VPN, commit by commit.

·1 min read
Business

Claude vs ChatGPT for Building Agents: The Decision Nobody Explains Properly

Most builders choose their LLM by inertia or by what they read on Twitter. But building profitable AI agents in 2026 requires something more specific: choosing the right model based on task type, not hype. Here's the framework I use.

·1 min read
Programming

8 Tools, 1 Stack, 0 Surprises: The Complete Indie Hacker Architecture for 2026

Most indie hackers don't lose time building — they lose it integrating tools nobody designed to work together. In 2026 there's an 8-tool stack that covers everything from database to social automation, frictionlessly and without rewrites. Here's the complete architecture, with the concrete patterns that make the difference.

·1 min read
Business

Your WADM Matrix Weights Are Lying to You (And How to Tell)

Most entrepreneurs fill out the WADM matrix with the weights they think they have. The problem: there's a brutal gap between what you say you value and what you actually weight when evaluating an idea. This article shows you how to spot that gap before it costs you months.

·1 min read
Programming

Claude Skills: The 3-Level System That Turns Claude into a Domain Expert (Without Retraining)

Most people use Claude like a generic assistant. But there's a whole layer—Skills—that transforms Claude into an expert for your specific workflow, loading procedural knowledge on-demand with a 3-level architecture built for efficiency. Here's how it works and how to build your own.

·1 min read

The Book That Made Me Stop Consuming and Start Producing (And Why It Changes Everything)

There's a book on financial mindset that most people ignore because the title sounds like an empty promise. But inside is a framework that completely reorders how you think about money, time, and business. Here's what I found.

·1 min read
Projects

The Algorithm That Decides Who Gets Into the Directory (And Why It Matters When Water Is Rising)

Building an emergency plumber directory is easy. Building one you can actually trust at 2am with a burst pipe is a different story. Here's the logic behind find-emergency-plumber.com's quality system, and what you can learn to vet service providers yourself.

·1 min read
Business

The Email They Almost Deleted: The 3 Metrics That Made Mailchimp a Giant (And That Your SaaS Is Probably Ignoring)

Mailchimp took 20+ years to reach its massive Intuit acquisition, with founders retaining 100% ownership. It wasn't luck—it was NRR, Rule of 40, and expansion revenue. Here are the real numbers that separate SaaS companies worth a fortune from those barely surviving.

·1 min read
Programming

Claude Agent SDK: 4 Patterns That Separate a Real Autonomous Agent from a Glorified Chatbot

Most developers build 'agents' that are, at their core, API calls with some conditional logic wrapped around them. Claude Agent SDK in 2026 proposes something fundamentally different: systems that gather context, act, verify their own work, and repeat the cycle autonomously. Here are the 4 concrete patterns that make that difference.

·1 min read

The Framework That Asks You to Imagine Failure (Before It Happens)

Most builders analyze failed projects after they die. The Pre-Mortem inverts that logic: you imagine the project has already failed, before you even start. The result is counterintuitive but powerful: more failure causes are identified than with any other planning technique.

·1 min read
Projects

What Building a Church Website Taught Me About Designing for Real Users

CCL Guadalajara is not a SaaS, generates no leads, and has no conversion metrics to report. And that's exactly why it was one of the most useful projects I've built in 2026: it forced me to design software for users who are not developers. Here's what I learned.

·1 min read
Business

The Margin Gap That Determines What Your Business Is Worth the Day You Sell It

The average physical business operates on margins of just 2.8-3.5%, while a digital course can hit 85-95%. But the real difference isn't in monthly profit—it's in what your company is worth the day you decide to exit. Here's the math that completely changes how you should think about what you build.

·1 min read
Projects

I Built a 6-Agent AI System to Publish Content Automatically. Here's How the Architecture Works.

I had 2,163 CNAE/IAE codes to cover and zero time to do it manually. The solution was a multi-agent system with Claude that orchestrates filtering, planning, writing, publishing, and social distribution autonomously. Here's how it's built, decision by decision.

·1 min read
Business

If Anyone Can Do It, No One Should: The CENTS Commandment We Keep Ignoring

34% of online businesses fail because they build something nobody wants. But there's a second, equally silent mistake: building something anyone can already do. MJ DeMarco's CENTS framework has a direct answer for this—and most entrepreneurs don't apply it until it's too late.

·1 min read
Programming

500K Free Invocations Per Month: What Supabase Edge Functions Actually Change in Your Stack (That Nobody's Talking About)

Supabase Edge Functions isn't just 'another way to write serverless'. With the Deno 2.1 runtime, dashboard-native testing, and a generous free tier, it fundamentally changes how you ship backend logic without leaving the ecosystem. Here's the real case, with code.

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Second-Level Thinking: Why Almost Every Builder Makes the Wrong Decisions (And Doesn't Even Know It)

Howard Marks built one of the world's largest investment firms with a single edge: thinking differently—and better—than everyone else. This week, after covering Munger and Naval, I close the trilogy with the framework that's most changed how I evaluate every product decision.

·1 min read
Projects

I Built a Free Tool for Spanish Tax Authorities. Then I Had to Decide Whether to Kill It or Monetize It.

Conversor IAE CNAE started completely free. With 2,247 dynamically generated pages and real SEO traffic, the uncomfortable question arrived: how do you generate revenue without destroying what made the product useful? Here's the real monetization architecture I built: three layers, zero paid advertising, and the technical decisions behind each one.

·1 min read
Business

The Number Entrepreneurs Ignore Before Launching (And That Predicts Whether Anyone Will Pay)

34% of startups fail because they build something nobody wants. But there's a public, free, and brutally honest data point that predicts whether your market has real buying intent before you write a single line of code: CPC. Here's how to read it correctly.

·1 min read
Programming

5ms vs 200ms: Why Cloudflare Workers Changes What You Can Build (Not Just What You Pay)

Most developers see Cloudflare as a cheaper AWS alternative. They're looking in the wrong direction. The real difference isn't in cost — it's in the V8 isolate architecture that makes your product literally faster than competitors who pay more. Here's why in 2026 this is no longer optional.

·1 min read

Nobody Asks How Hard Buffett Works: The Naval Framework Everyone Ignores

Most people optimize for effort. Naval Ravikant has been saying for years that's exactly the mistake. Judgment—not hustle—is what separates those who build wealth from those who merely accumulate hours. Here's the complete framework and how to apply it in 2026.

·1 min read
Projects

I Analyzed Every Spanish Gestoría Directory and They All Fail the Same Way

When I started building Gestorías Cerca de Mí, the first thing I did was analyze what already existed in the market. What I found was surprising: it's not that directories don't exist, it's that they all make exactly the same mistakes. Here's the full analysis and the technical decisions I made to build something different.

·1 min read
Business

The Complete Map of Online Business Buy/Sell Platforms in 2026 (And the Signal Nobody Reads Correctly)

Building from scratch isn't the only path to a profitable online business. A mature acquisition market exists where current multiples are near historic lows, creating a real window for buyers. The problem is most people don't know how to read the right signals or choose the right platform for their profile.

·1 min read
Programming

From Scrapy to Apify: The Real Case Study That Made Me Rethink How I Build Production Scrapers

Daltix went from managing EC2 servers to scaling to 5 million resources per day while cutting infrastructure costs by 90%. It wasn't magic — it was switching to the right tool at the right time. Here's when that switch makes sense and how Apify works under the hood.

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Munger's Mental Test Before Forming Any Opinion: The Ideology Trap That Destroys Good Decisions

Charlie Munger had a strange rule: before forming any opinion, he had to be able to argue the opposing side better than its own advocates. Few people pass that test. Here's why that changes everything, and how to apply it to your decisions as a builder.

·1 min read
Projects

I Built a VPN to Compete with NordVPN. Here's What I Learned.

Everyone tells you that you can't compete with NordVPN or ExpressVPN. And they're right... if you try to be them. NautilusVPN was born from a different question: what niche are the giants ignoring? This is the build, the real technical decisions, and what it means to launch a SaaS in a market that seems impossible.

·1 min read
Programming

Free Production Stack: Everything Included in Vercel Hobby + Cloudflare Free (And What Nobody Tells You)

Vercel Hobby and Cloudflare Free together form one of the most powerful stacks you can build without spending a cent. But there's an SSL configuration mistake that catches almost everyone on their first attempt, and limits you need to know before launching anything serious. Here's everything, with the exact DNS records and the fix nobody documents properly.

·1 min read

You Don't Need More Discipline. You Need Better Architecture.

Everyone tells you to set better goals. Nobody tells you that goals might be the problem. Donella Meadows spent decades studying complex systems and found something uncomfortable: most of us push change in exactly the wrong direction.

·1 min read
Business

WADM vs Intuition: When to Trust the Matrix and When to Follow Your Gut

The WADM Matrix is a brilliant tool for evaluating business ideas, until it becomes a trap for postponing decisions. In 2026, the real skill isn't knowing how to use the framework: it's knowing when to ignore it.

·1 min read
Programming

Your First MCP Server in Python: The 3 Primitives Every Tutorial Ignores

November 2024. Anthropic quietly launched MCP. Now in 2026, there are 270+ servers in production and companies like Block and Apollo use it in their stacks. The problem: most tutorials only teach you one of the protocol's three primitives. Here you'll see all three, with real Python code.

·1 min read
Programming

Edge vs Serverless on Vercel: The Architecture Mistake Nobody Warns You About (Until It's Too Late)

I spent months deploying functions on Vercel without truly understanding the difference between Edge and Serverless. When I finally got it, it changed how I structure every project. Here's exactly what they are, when to use each, and how to make that decision before writing your first line of code.

·1 min read

The Most Successful Share Everything. The Struggling Guard Their 'Secrets'. Neuroscience Explains Why.

It's not about generosity or strategy. Entrepreneurs who win long-term are literally running a different mental operating system—one that processes failure, competition, and time in radically different ways. In 2026, with more noise than ever, understanding these three mental patterns is the most underestimated competitive advantage.

·1 min read
Business

4 Types of AI Agents You Can Monetize Right Now (And the One Nobody Is Building)

The AI agent market grows at 45.3% annually with projections reaching $103.6B by 2032. Everyone talks about text chatbots. But there's a category growing even faster, with less competition, and barely anyone in Spain is touching it: voice agents.

·1 min read
Programming

The Vercel Bill Nobody Expects: The 5 Factors That Actually Determine Your Next.js Costs

Every Next.js developer thinks they understand Vercel's pricing until the first bill arrives. The problem isn't the price—it's that nobody explains the five metrics that actually control what you pay, and which one completely changes the game for AI workloads in 2026.

·1 min read
Projects

The Most Valuable Lead in the Market Isn't the Most Searched: It's the Most Desperate

There's a brutal difference between a regular plumbing lead and an emergency one at 3 AM. It's not a volume difference—it's an urgency difference. And that urgency changes absolutely everything: the price, the technical architecture, and the business strategy behind find-emergency-plumber.

·1 min read
Business

The Number That Destroys Your SaaS Before You See It Coming (and How to Fix It)

Most SaaS founders obsessed with acquiring new customers are ignoring the number that determines whether their business is worth a fortune or almost nothing: Net Revenue Retention. The difference between being above or below 90% isn't linear. It's abysmal.

·1 min read
Programming

Resend Isn't Just 'SendGrid with Better UX': What I Discovered Building a Batch Email System in 2026

Most devs use Resend for simple transactional emails and stop there. But when I started building a bulk notification system, I discovered it has a completely different batch architecture — with limits, superpowers, and traps nobody explains. Here's what I learned from the trenches.

·1 min read

Why the Smartest People Choose the Wrong Path (And the Book That Explained It All)

There are three roads to wealth. Intelligent pessimism—that voice that sounds like prudence—is exactly what pushes the most capable people toward the slowest path. The Millionaire Fastlane explains it better than any other book I've read in 2026.

·1 min read
Programming

I Launched My SaaS, Set Up Stripe… and Was Losing 30%+ of Recurring Revenue Without Knowing It

Your Stripe integration isn't done when the first payment goes through. There are two silent holes bleeding your MRR from day one: failed payments you never recover and users who churn because they can't manage their own subscription. Here's how to close both with Smart Retries and the Customer Portal.

·1 min read

3 Decision Frameworks Used by a Fighter Pilot, a General, and Elon Musk (And None Are What You Expect)

Over 15 frameworks exist to compress decades of wisdom into repeatable processes. Most people use none of them. These three transformed military strategy, massive-scale corporate decisions, and zero-to-one technological innovation.

·1 min read
Projects

I Had the Wrong CNAE Code From Day One (And Didn't Even Know It)

Thousands of freelancers and SMEs in Spain operate with incorrect IAE or CNAE codes without realizing it, losing access to grants and risking penalties from the tax authority. In this article I explain the real difference between both systems, the most common classification errors, and how to use a converter to ensure your business is correctly registered in 2026.

·1 min read
Business

The Margin Gap Nobody Calculates Before Going Online (And Why It Changes Everything)

Online courses operate at 85-95% margins while physical retail barely hits 2.8-3.5%. That 30x gap isn't just an accounting detail—it's why two entrepreneurs with the same effort can end up in completely different economic worlds. Here's the structure behind that gap.

·1 min read
Programming

Late API: 60 Req/Min Free and a Single Call to Publish on 12 Platforms

I just found out Buffer has no public API. None at all. While searching for an alternative, I found Late: an API that publishes to 12 platforms with a single POST call, offers full API access free from day one, and has delivered over 2.3 million posts with 99.97% uptime. This changes how I build content tools.

·1 min read

Howard Marks Has Been Saying the Same Thing for Decades. Nobody Applies It to Their Products.

Howard Marks isn't just a legendary investor: he's the best teacher of cyclical patterns in existence. In 2026, while everyone debates whether AI is a bubble or a real takeoff, his framework on inevitable cycles answers exactly when to act and when to wait. And it applies equally to markets and products.

·1 min read
Projects

Why Most Local Directories Have a UX Problem (And How I Fixed It in Gestorías Cerca de Mí)

Most local directories are designed for Google's crawler, not for the human who needs to find a gestoría in 2 minutes. In this article I share the specific UX decisions I made in Gestorías Cerca de Mí to serve both, and why some of those decisions go completely against what you'd do if you were only thinking about SEO.

·1 min read
Business

The 10-Year Idea Test: The Validation Question Nobody Asks (And the Only One That Matters)

Everyone validates whether their idea will sell in month one. Nobody validates whether it will still be selling in year ten. There are two completely different types of validation, and confusing them is why only 34.9% of businesses survive a decade.

·1 min read
Programming

3 Projects in Sanity, 3 Different Pricing Decisions: What Nobody Explains About Its Tiers

Sanity's free tier is genuinely generous, but most developers don't know exactly when they need to upgrade. Here's what I learned building real projects: a personal SaaS, a client project, and a team content platform.

·1 min read

The Naval Ravikant Question That Changes How You Make Decisions Forever

Naval Ravikant has a mental trick that isn't about money—it's about clarity. It's about setting an hourly rate so high it embarrasses you... and then using it as a filter for every decision in your day. I applied it for months and it changed everything.

·1 min read