Justin Castillo
Contact
Software Architect — San José, Costa Rica

I build softwarebusinesses actually use.

Tailored web apps, internal tools, and AI integrations for companies that need software shaped to how they work — not the other way around.

Start a projectI'm a developer
Experience

Where I've worked

  1. Jan 2023Present3Y 8M

    Senior Software Engineer

    Moody's · San José, Costa Rica (Hybrid)

    • Design and build financial data services used across the organization
    • Lead delivery of full-stack features with TypeScript, React, and AWS
    • Drive adoption of AI-assisted engineering workflows on my team
    TypeScriptReactNode.jsPostgreSQLAWS
  2. Jan 2022Jan 20231Y 1M

    Blockchain Developer

    BrainDAO · Remote (Decentralized)

    • Built smart contracts and dApps for the IQ token ecosystem
    • Developed governance and staking tooling for the DAO
    SolidityTypeScriptNext.jsEthereum
  3. May 2021Jan 20231Y 9M

    Full-Stack Blockchain Developer

    IQ.wiki · Los Angeles, California, US (Remote)

    • Helped rebuild the world's largest crypto encyclopedia on a modern web stack
    • Integrated wallet authentication and on-chain features into the platform
    TypeScriptNext.jsGraphQLNestJSEthereum
  4. May 2022Sep 20225M

    Education Committee Member

    AsoBlockchain Costa Rica · Costa Rica

    • Helped expand blockchain knowledge in Costa Rica — cryptocurrencies, smart contracts, NFTs, and DeFi — through talks and community programs
  5. Dec 2020May 20216M

    Blockchain Application Developer

    EOS Costa Rica · Costa Rica

    • Built EOSIO-based applications and smart contracts for enterprise clients
    • Contributed to open-source blockchain tooling
    EOSIOC++Node.jsReact
  6. Mar 2020Nov 20209M

    Software Intern

    EOS Costa Rica · Costa Rica

    • Shipped full-stack features across web applications alongside senior engineers
    JavaScriptReactNode.js
  7. Nov 2016Mar 20203Y 5M

    Full-Stack Engineer

    Comunidad Aplicaciones Móviles – ITCR · Florencia, Santa Clara, Costa Rica

    • Built web and mobile apps for community and campus projects
    • Mentored fellow students on software development practices
    AndroidJavaAngularFirebase
  8. Feb 2017May 20174M

    Android Developer

    Comunidad de Móviles TEC SSC · Santa Clara, San Carlos, Costa Rica

    • Built Android apps and ran hands-on workshops for the student community
    AndroidJava
Credentials
B.Sc. Computer Engineering — Tecnológico de Costa Rica, 2016–2020Claude Code in Action — AnthropicModel Context Protocol: Advanced Topics — AnthropicRetrieval Augmented Generation — DeepLearning.AI
Services

What I build

Custom web applications

Customer portals, booking systems, dashboards — full-stack apps built around your workflow, not a template.

Internal tools & automation

Replace the spreadsheet maze: inventory, reporting, and operations tools your team actually wants to open.

AI integrations

Claude-powered assistants, document processing, and RAG search wired safely into your existing systems.

Ongoing support

I stay after launch — monitoring, fixes, and improvements as your business changes.

For developers

You can already build. Selling is the other half.

Most of us learned to ship software and nothing about finding the people who will pay for it. The engineering was never the hard part — writing the offer, naming a price out loud, and following up without feeling like a nuisance is. That gap is what this part of the site is about.

Positioning

Stop being "a full-stack developer" and become the person a specific business calls for a specific problem. Narrow beats broad every time.

Pricing

Move off hourly. Price the outcome the client is buying instead of the time you spend, and learn to say the number without apologising for it.

Finding clients

Where the work actually comes from — referrals, a portfolio that answers objections, and outreach that reads like a person wrote it.

Running the engagement

Scoping, contracts, deposits, and the boundaries that keep a project from quietly turning into unpaid work.

Published

The Hormozi offer system, in Spanish and inside your terminal

I translated hormozi-skills-es into Spanish — Alessandro Smedile's offer skills library: 18 skills and 6 agents that run in Claude Code or Codex and turn an idea into a complete offer, covering market, pricing, objections, pitch and landing page copy. It is free and MIT licensed. I use it myself to build my own consultancy.

Install the skill
Contact

Let's build something.

Tell me what's slowing your business down. I'll tell you if software can fix it.

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