Oscar Fonseca

Senior Full-Stack & Web3 Engineer

Account Abstraction (ERC-4337) | DeFi Financial Engineering | Protocol Design

Current Focus: Building GasX — A no-code gas sponsorship platform on ERC-4337.
Designing systems with adoption, cost, and ops in mind.

I design and ship end-to-end blockchain products with a strong focus on:

• User Adoption: Reducing friction in onboarding flows.
• Cost Optimization: Managing gas and infrastructure overhead.
• Operational Simplicity: Building systems that are viable to operate in production.

My work spans smart contracts, backend infrastructure, and frontend delivery. I bridge the gap between product requirements and technical execution, taking products from idea → prototype → production under real constraints.

• Financial Engineering in DeFi (markets, incentives, on-chain primitives)
• Account Abstraction (ERC-4337) & Gas Sponsorship
• Designing protocols with real operational constraints
• Shipping fast under pressure (hackathons, short timelines, limited resources)

I consistently validate ideas through hands-on building, often learning new stacks or languages on the fly when the problem demands it.

Role: Lead Architect & Developer

A no-code gas sponsorship platform built on Account Abstraction (ERC-4337), designed to reduce user friction and operational complexity for Web3 products.

GasX allows product, growth, and DAO teams to:

• Launch gasless user onboarding campaigns.
• Manage sponsorship budgets and white-label experiences.
• Avoid complex SDK-level integrations.
• Ship faster with lower infrastructure overhead.

Tech Stack: Solidity, Foundry, Next.js, TypeScript, AWS, PostgreSQL.

I believe the fastest way to learn and validate ideas is by building real systems under pressure.

An on-chain prediction market with custom oracles and a composable AMM, integrated with Tapp Exchange and Nodit for live data.

• Highlight: Designed and shipped a full dApp while ramping up on the Move language in a short timeframe.
• Stack: Move, Aptos SDK, TypeScript, Next.js, Tailwind, Zustand, Go, Prisma, Supabase.

An on-chain protocol for verifiable clinical audit trails in the Decentralized Science (DeSci) space.

• Highlight: First place winner, recognized for real-world applicability and protocol design.
• Stack: Solidity, Next.js, TypeScript, Hardhat, Prisma, Supabase, PostgreSQL.

An airdrop platform focused on community building instead of mercenary incentives.

• Highlight: Delivered a production-ready mini-app on Base L2 with real user flows.
• Stack: Solidity, Base, Base Account, Farcaster API, Neynar, AWS.

const oscarFonseca = {
  role: "Full-Stack & Web3 Engineer",
  focus: [
    "Account Abstraction",
    "DeFi Financial Engineering",
    "Protocol & Infrastructure Design",
    "Gas & Cost Optimization"
  ],
  technologies: {
    blockchain: [
      "Solidity", "Move", "Hardhat", "Foundry",
      "OpenZeppelin", "Aptos SDK"
    ],
    frontend: [
      "React", "Next.js", "TypeScript",
      "TailwindCSS", "shadcn/ui"
    ],
    backend: [
      "Node.js", "NestJS", "Go"
    ],
    infra: [
      "AWS", "GCP", "Docker", "Kubernetes", "GitHub Actions"
    ],
    databases: [
      "PostgreSQL", "MySQL", "MongoDB", "Redis"
    ],
    exploring: [
      "Rust", "Solana", "Zero Knowledge (ZK)",
      "LLMs & Automation", "n8n"
    ]
  }
};