Hello, I'm

Andrés Castillo

I build performant, scalable web applications and integrate AI-driven solutions to solve complex real-world problems and deliver exceptional user experiences.

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About Me

Engineering intelligent, scalable web experiences.

I'm a Web Architect who designs end-to-end systems across diverse industries and complex business domains. My work sits at the intersection of modern web engineering and AI — not as separate disciplines, but as a unified approach to building smarter software.

I specialize in turning complex business problems into clean, maintainable architectures — increasingly enhanced by AI-assisted development workflows. Beyond code, I invest in growing engineering teams through technical leadership, community building, and hands-on mentoring.

12+ years experience Medellín, Colombia

Skills & Tools

Technologies I Work With

I believe in choosing the right tool for the job. Here are the technologies I use most frequently.

AI & Intelligent Systems

  • Prompt Engineering
  • RAG / Embeddings
  • LLM Integration (Claude, OpenAI)
  • Ollama / Local Models
  • pgvector
  • AI-Assisted Development (Cursor, Claude Code)

Frontend

  • React / Next.js
  • Svelte / SvelteKit
  • Vue.js / Nuxt
  • JavaScript / TypeScript
  • Tailwind CSS
  • HTML5 / CSS3

Backend

  • Node.js
  • NestJS
  • Python / Django
  • Go
  • REST & GraphQL
  • WebSockets

Database

  • PostgreSQL
  • MongoDB
  • Redis
  • Prisma / Drizzle
  • MySQL
  • Supabase

Cloud & DevOps

  • AWS / GCP
  • Docker
  • CI/CD Pipelines
  • Vercel
  • Terraform
  • GitHub Actions

Selected Work

Projects I've Built

Each project represents a unique challenge. I focus on clean code, performance, and delivering real value.

Screenshot of Budget

Budget

Personal finance app for tracking income, expenses, bills, and budgets with dashboard analytics. Features Google OAuth, multi-currency support, and AI-powered financial insights coming soon.

SvelteKit NestJS MongoDB Tailwind CSS AI
Screenshot of BarrioAlerta

BarrioAlerta

In Development

Neighborhood safety app for Colombian cities that replaces chaotic WhatsApp security groups with a structured incident map, verified neighbor network, smart proximity alerts, and weekly barrio safety trends.

React Native Node.js PostGIS Firebase
Screenshot of FincaSegura

FincaSegura

In Development

WhatsApp-first booking platform with escrow payment protection for vacation finca rentals in Colombia. Solves rampant scam problem by onboarding rural owners via WhatsApp bot and holding guest payments in escrow until verified check-in.

Next.js Supabase WhatsApp API Wompi
Screenshot of CargaCO

CargaCO

In Development

Colombia's unified EV charging platform. Aggregates fragmented charger networks into a single live map with real-time availability, reservations, and COP-native payments via Nequi and PSE. Includes a B2B CPO dashboard for malls, hotels, and parking operators to monetize their chargers with dynamic pricing and utilization analytics.

React Native Next.js Node.js PostgreSQL OCPP
Screenshot of FacturApp

FacturApp

In Development

WhatsApp-first electronic invoicing for Colombian micro-businesses and freelancers. Simplifies DIAN compliance by handling XML generation (UBL 2.1), CUFE signing, real-time DIAN transmission, and client-ready PDFs — all from a simple chat message. Includes digital certificate management, frequent client directory, and a multi-NIT dashboard for independent accountants.

WhatsApp API Node.js DIAN UBL 2.1 SaaS Fintech
Screenshot of ObraLog

ObraLog

In Development

WhatsApp-native field documentation app for Colombian construction subcontractors. Turns scattered phone photos into geotagged, timestamped evidence organized by project — generating daily progress reports and payment-ready PDF packets to eliminate disputes.

React Native Firebase WhatsApp API Android
Screenshot of ArriendoOS

ArriendoOS

In Development

Rental management platform for Colombian small landlords (2–9 units). Automates rent collection via WhatsApp + Nequi/PSE, calculates Ley 820 IPC annual increases, generates paz y salvo documents, and gives tenants a downloadable payment history certificate — replacing the cuaderno-and-WhatsApp chaos with a lightweight dashboard.

React Node.js PostgreSQL WhatsApp API Wompi

// latest posts

From the Blog

Thoughts on development, design, and building better software.

React Architecture

[Building Scalable React Applications]

[Learn the patterns and best practices for creating React applications that scale well with your team and codebase.]

March 10, 2026 8 min read
TypeScript JavaScript

[Mastering TypeScript Generics]

[A deep dive into TypeScript generics, from basic concepts to advanced patterns that will level up your type safety.]

February 28, 2026 12 min read
CSS Frontend

[Modern CSS Techniques for 2026]

[Explore the latest CSS features including container queries, cascade layers, and the new color functions.]

February 15, 2026 6 min read
View All Posts

Contact

Let's Work Together

Have a project in mind or just want to chat? Drop me a message and I'll get back to you as soon as possible.

Currently open to freelance opportunities and exciting full-time roles. Available for remote work worldwide.