Portrait of Nicolas Fainstein

Nicolas Fainstein

I design and ship web3 products end to end. Most recently I led the cross-chain module of the Ethereum Foundation's Interop SDK.

Buenos Aires (GMT-3) · 4+ years in web3 · Remote

See my work
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Featured Work

Interop SDK, desktop view
Interop SDK, mobile view

Ethereum Foundation · Wonderland

Interop SDK

Led design and implementation of the cross-chain module

A TypeScript SDK that unifies five cross-chain bridging providers (Across, LiFi, Relay, Bungee, OIF) behind a single API, built at Wonderland for the Ethereum Foundation alongside OpenZeppelin. #1 committer with 130 commits: I built provider integrations, owned the e2e infrastructure (Playwright against a forked network in CI) and the release cycle, and ran the engineering response to two autonomous security audits, overturning wrong verdicts and patching gaps the vendors missed.

  • TypeScript
  • viem
  • Monorepo
  • CI e2e on forked networks
interopaddress.com (opens in new tab)benchmark.interop.wonderland.xyz (opens in new tab)Open Source (repository, opens in new tab)
Balmy, desktop view
Balmy, mobile view

Onchain neobank

Balmy

Frontend engineer, led the rebranding and design system

A web3 home-banking app: swaps, yield earning, DCA, transaction history, contacts and multi-wallet support. I drove the full rebranding, built the design system in Storybook, and integrated the yield aggregator (Aave, Beefy, Yearn) through REST APIs.

  • React
  • TypeScript
  • Redux
  • Storybook
  • ethers.js
  • viem
balmy-demo.vercel.app (opens in new tab)Open Source

Growth

  1. 2025-2026

    Wonderland · Technical Lead

    I led the cross-chain module of the Interop SDK as its #1 committer, owned the release cycle, and worked with the Ethereum Foundation and OpenZeppelin.

  2. 2023-2025

    Balmy · Frontend Engineer

    I drove the rebranding of a web3 neobank, built its design system in Storybook, and integrated yield aggregators.

  3. 2023

    La Nación · Frontend Engineer

    I built real-time election stats for one of Argentina's biggest news sites and worked on its TypeScript migration.

  4. 2022

    Apeel Sciences · Software Engineer

Projects

TornadoCodes

Aleph Hackathon 2024 · 1st place / 54 teams

An address-free access layer for crypto payments, built with a teammate: ZK commitments and nullifiers (Pedersen hashes, Merkle trees) power claim codes, gift cards and airdrops without asking anyone for a wallet address first.

dorahacks.io/buidl/15187 (opens in new tab)

credora

Side project · Sepolia

A DeFi lending protocol built end to end, solo: six Solidity contracts with Groth16 proof verification before issuance, ERC-721 notes with fully on-chain metadata, and fork tests. Deployed and verified on Sepolia, consumed from a wagmi frontend that submits the proof.

github.com/nicofains1/credora (opens in new tab)

Open to senior full-stack and frontend roles.

Remote or Buenos Aires (GMT-3)

GitHub