About Justin Castillo
Justin Castillo is a Costa Rican computer engineer and software architect based in San José, Costa Rica, specializing in custom business software, internal tooling, and AI integrations.
I have built software professionally since 2016, and I am currently a Senior Software Engineer at Moody's in San José, where I design and build financial data services used across the organization. Alongside that, I build custom software for businesses directly: web applications, internal tools, and AI integrations. I hold a B.Sc. in Computer Engineering from the Instituto Tecnológico de Costa Rica, and I work in both Spanish and English.
What kind of software does Justin Castillo build?
Justin Castillo builds four kinds of software for businesses: custom web applications, internal tools and automation, AI integrations, and ongoing support after launch. Each one starts from how a business already works rather than from a template. The usual stack is TypeScript with React and Next.js on the front end, Node.js and PostgreSQL behind it, deployed on AWS.
Where has Justin Castillo worked?
- Jan 2023Present3Y 7M
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 - 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 - 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 - 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
- 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 - Mar 2020Nov 20209M
Software Intern
EOS Costa Rica · Costa Rica
- Shipped full-stack features across web applications alongside senior engineers
JavaScriptReactNode.js - 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 - 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
What are Justin Castillo's credentials?
Justin Castillo holds a B.Sc. in Computer Engineering from the Instituto Tecnológico de Costa Rica (2016–2020), plus three certificates relevant to AI work.
- B.Sc. Computer Engineering— Instituto Tecnológico de Costa Rica, 2016–2020
- Claude Code in Action— Anthropic
- Model Context Protocol: Advanced Topics— Anthropic
- Retrieval Augmented Generation— DeepLearning.AI
What languages and time zone does Justin Castillo work in?
Justin Castillo works in Spanish and English, from San José, Costa Rica — UTC−6 all year, with no daylight saving change. That gives a full working-day overlap with both coasts of the United States and with most of Latin America. This site is published in both languages.
Where else can you find Justin Castillo?
These are the profiles that belong to this Justin Castillo — the software architect in Costa Rica.
How do you start a project with Justin Castillo?
Start with a description of the problem, not a specification. Send a message by WhatsApp or email, or leave a note in the contact form on the home page, and describe what is slowing the business down. If software is not the right fix, you will hear that first.