Julien Béranger — Smart Contract & Full-Stack Engineer

Julien Béranger

+ Claude Sonnet 5

Profile

Full-stack and smart contract developer with 6+ years of production experience, most of it on Solidity and the Ethereum Virtual Machine (EVM). Experienced in designing token registries and on-chain issuance systems for institutions (including a registry built for AFNIC, which manages 4 million .fr domain names), an expert in Foundry for contract testing (fuzzing, invariants), and comfortable working on permissioned EVM chains and their upgradeable system contracts. Fluent English, used daily in international settings.

Key skills

  • Solidity & EVM: design and development of smart contracts in Solidity, using OpenZeppelin libraries for token standards (including ERC-20) and NFTs.
  • Advanced testing: Foundry expert — fuzz testing and invariant testing are at the core of my day-to-day practice — complemented by Jest integration tests and CI/CD pipelines.
  • Security & robustness: at Arthera, improved the core protocol through load-testing campaigns and upgrades to upgradeable system contracts; designed privacy-preserving APIs using zero-knowledge proofs at W3HC.
  • Enterprise EVM chains: solid conceptual understanding of permissioned EVM architectures such as Hyperledger Besu; familiar with the Canton Network and its Zenith EVM execution layer, whose privacy-by-partitioning approach echoes the anonymous-API work done at W3HC — able to ramp up quickly on both stacks where needed, using standard Solidity tooling (Foundry, Ethers.js) against Zenith's EVM-compatible RPC.
  • Web3 tooling: Ethers.js, Viem, Wagmi, Reown.
  • English: daily working language (technical documentation, workshops, support for international developers).

Professional experience

CEO & Lead Developer — Strat (2020 – present)

  • Designed an NFT registry for AFNIC, the institution managing 4 million .fr domain names — direct, hands-on experience issuing tokens for an institutional trusted third party.
  • Developed several Web3 projects for Kleros and Hexarchia.
  • Delivered a custom RAG system for Systemlog (5,000+ monthly active users).
  • Won 1st prize at the DAO Global Hackathon 2022, Core DAO technical track.
  • Ran Web3 hackathons for UNESCO and Paris 8 University; trained students at Epitech, STUDI, and emlyon business school.

Co-founder & Lead Developer — W3HC (February 2023 – present)

  • ZK API: TypeScript implementation of a zero-knowledge cryptography research proposal, enabling anonymous API access — an approach directly transferable to the privacy requirements of a network like Canton.
  • w3pk: passwordless Web3 authentication SDK.
  • Gov: cross-chain, on-chain voting system.
  • Rukh: agentic RAG service built in Nest.js.
  • Implemented the game of Go in Solidity (a rigor exercise in contract logic).

Developer Relations Engineer — Arthera (July – December 2023)

  • Improved the core product through load testing and upgrades to upgradeable system contracts — work directly transferable to the robustness and security requirements of a tokenization infrastructure.
  • Wrote technical documentation, guides, and app examples; provided technical support online and at hackathons.
  • Supported partners integrating the product; organized a 150+ attendee event during EthCC 2023 in Paris.

Developer Relations Engineer — Aurora Labs (September – December 2022)

  • Wrote technical documentation, guides, and app examples; provided developer support online and at hackathons on the Aurora stack.

CEO & CTO — Āto (2020 – 2022)

  • Designed the product together with an IP-specialized lawyer; managed a team of six developers in a fully remote environment.
  • Built an NFT marketplace and live NFT auction service, in Solidity and React.

Head of Communications — iExec (2016 – 2019)

  • Led the ICO, raising 10,000 BTC in under 3 hours.
  • Organized events (200+ attendees) during Devcon in Prague.

Other experience

  • Customer Support Manager — OpenClassrooms (2014 – 2016): built the customer service function from scratch, handling 1,000+ requests weekly.
  • Chinese teacher — French National Education (2008 – 2013).

Education

  • Degree in Chinese Studies (Philosophy, Literature and Arts) — INALCO (National Institute for Oriental Languages and Civilizations), Paris, 2007.

Languages

  • English: fluent, daily working language.
  • French: native.
  • Chinese: fluent (former Chinese teacher, Chinese Studies degree from INALCO).

Contact