Julian Ruiz — Blockchain Engineer | Smart Contracts & Web3 Full Stack Development | Solidity.

Expertise in Smart Contract (3.5 yr.), Full Stack Web (4.0 yr.).

Last verified on May, 2026

Core Skills

Solidity

4 yr.

Foundry

2 yr.

Bio Summary

Blockchain Engineer with 3+ years of experience in DeFi, smart contracts, and Web3 full stack development using Solidity, Foundry, React, TypeScript, wagmi, and viem.
Skilled in secure smart contract development, fuzz testing, invariant testing, mainnet fork testing, and static analysis with Slither and Aderyn.
Built scalable DeFi governance, vault, treasury, NFT, and subscription-based blockchain systems, plus fintech payment infrastructures integrating Binance APIs and microservices.
Experienced with ERC20, ERC721, and ERC4626 standards, decentralized voting systems, and full stack development using Node.js, Express, React, and REST APIs.

Technical Skills

Programming Languages	JavaScript, Solidity, TypeScript
JavaScript Libraries and Tools	Ethers.js, React Native
JavaScript Frameworks	Express, Node.js, React
Ruby Frameworks	Ruby on Rails
Salesforce Ecosystem	SalesForce Workflow
Data Analysis and Visualization Technologies	Celonis
Databases & Management Systems / ORM	PostgreSQL, Supabase
UI Frameworks, Libraries, and Browsers	Tailwind CSS
Azure Cloud Services	Azure VM
SDK / API and Integrations	API, API testing, RESTful API
QA, Test Automation, Security	API testing, Unit Testing, Usability tests
Blockchain and Decentralized Software	DeFi, ERC-20, ERC-721, Ethers.js, Foundry, Hardhat, MetaMask, OpenZeppelin, RainbowKit, Stellar, Viem, WAGMI
Methodologies, Paradigms and Patterns	microservices
Operating Systems	Unix
Mail / Network Protocols / Data transfer	WebSockets
Other Technical Skills	InterPlanetary File System, Slither

Work Experience

Full Stack Blockchain Engineer - Investment Armendariz (DeFi Platform - Governance, Vault Infrastructure, Treasury Systems)

Duration: Aug 2025 - Present
Summary:

A decentralized finance (DeFi) platform focused on governance, vault infrastructure, treasury systems, and on-chain operational controls
The platform aims to provide secure and scalable DeFi services with robust smart contract architecture and user-friendly Web3 integration

Responsibilities:

Develop Solidity smart contracts and support protocol architecture decisions across smart contracts, frontend, and Web3 integration layers.
Build modular frontend features using React, TypeScript, wagmi, viem, RainbowKit, and TailwindCSS.
Implement Foundry-based testing workflows including unit, fuzz, invariant, stateful, and mainnet fork testing.
Apply security analysis workflows using Slither and Aderyn to improve smart contract validation, maintainability, and protocol reliability.

Technologies: Solidity, Foundry, React, TypeScript, wagmi, viem, RainbowKit, TailwindCSS, Slither, Aderyn

Full Stack Developer - Vita Wallet (Fintech & Crypto Integrations Platform)

Duration: Oct 2021 - Nov 2025
Summary:

A fintech and crypto-related platform providing payment infrastructure, API integrations, backend services, and frontend applications
The platform integrates third-party APIs including Binance services to facilitate payment processing and transaction workflows

Responsibilities:

Developed and maintained platform features across payment infrastructure, API integrations, backend services, and frontend applications.
Integrated third-party APIs including Binance-related services.
Worked on backend services, microservices architecture, React frontend, React Native features, PostgreSQL workflows, and TypeScript/JavaScript codebases.
Improved platform stability and maintainability through unit testing, integration testing, debugging, production support, and performance improvements.

Technologies: React, React Native, TypeScript, JavaScript, Node.js, Express.js, PostgreSQL, Microservices, Binance API

Freelance Blockchain & Web3 Developer (Various Blockchain and Web3 Applications)

Duration: Dec 2021 - Present
Summary:

Designed and developed blockchain and Web3 applications focused on DeFi infrastructure, NFTs, tokenized platforms, governance systems, healthcare services, payment integrations, and decentralized applications
Projects include smart contracts and dApps with a focus on security and modern Web3 tooling

Responsibilities:

Built smart contracts using Solidity and OpenZeppelin standards including ERC20, ERC721, and subscription-based blockchain systems.
Developed decentralized applications using React, Ethers.js, wagmi, MetaMask, JSON-RPC flows, and modern Web3 tooling.
Implemented security-focused development workflows including smart contract testing, static analysis, fuzz testing, and validation practices.

Technologies: Solidity, OpenZeppelin, ERC20, ERC721, React, Ethers.js, wagmi, MetaMask, JSON-RPC, Hardhat, Foundry, Slither, Aderyn

Technical Instructor | Full Stack Development - Henry (Full Stack Software Engineering Mentorship)

Duration: Jan 2023 - Present
Summary: Mentorship program for students in full stack software engineering projects covering backend architecture, REST APIs, frontend development, database design, authentication, and scalable application architecture.
Responsibilities:

Mentored students in backend architecture, REST APIs, frontend development, database design, authentication, and scalable application architecture.
Provided technical guidance on Node.js, Express.js, React.js, RESTful APIs, frontend/backend integration, debugging, and maintainable development workflows.

Technologies: Node.js, Express.js, React.js, REST APIs

Education

London School of Commerce
English Language and Literature
2025

Certification

Cyfrin Updraft
Smart Contract Security
2024 - 2025
Henry
Full Stack Developer Program
2021
Platzi
Blockchain and Cryptocurrency School
2021 - 2022

How to hire with Upstaff

1

Talk to Our Talent Expert

Our journey starts with a 30-min discovery call to explore your project challenges, technical needs and team diversity.

2

Meet Carefully Matched Talents

Within 1-3 days, we’ll share profiles and connect you with the right talents for your project. Schedule a call to meet engineers in person.

3

Validate Your Choice

Bring new talent on board with a trial period to confirm you hire the right one. There are no termination fees or hidden costs.

Why Upstaff

Upstaff is a technology partner with expertise in AI, Web3, Software, and Data. We help businesses gain competitive edge by optimizing existing systems and utilizing modern technology to fuel business growth.

Real-time project team launch

<24h

Interview First Engineers

Upstaff's network enables clients to access specialists within hours & days, streamlining the hiring process to 24-48 hours, start ASAP.

x10

Faster Talent Acquisition

Upstaff's network & platform enables clients to scale up and down blazing fast. Every hire typically is 10x faster comparing to regular recruitement workflow.

Vetted and Trusted Engineers

100%

Security And Vetting-First

AI tools and expert human reviewers in the vetting process is combined with track record & historically collected feedbacks from clients and teammates.

~50h

Save Time For Deep Vetting

In average, we save over 50 hours of client team to interview candidates for each job position. We are fueled by a passion for tech expertise, drawn from our deep understanding of the industry.

Flexible Engagement Models

Custom Engagement Models

Flexible staffing solutions, accommodating both short-term projects and longer-term engagements, full-time & part-time

Unique Talent Ecosystem

Candidate Staffing Platform stores data about past and present candidates, enables fast work and scalability, providing clients with valuable insights into their talent pipeline.

Transparent

$0

No Hidden Costs

Price quoted is the total price to you. No hidden or unexpected cost for for candidate placement.

x1

One Consolidated Invoice

No matter how many engineers you employ, there is only one monthly consolidated invoice.

Ready to hire Julian Ruiz
or someone with similar Skills?

Book a call with Julian Ruiz

Start Hiring