Backend Software Engineer

Appsierra Group; Brussel; Sur place; EUR 120 000 - 180 000; Plein temps

Résumé du poste

Appsierra Group is seeking an experienced blockchain engineer to lead backend integration with smart contracts, wallets and dApps across the EU region. The role requires deep hands-on expertise in Ethereum, Hyperledger Besu, Solidity and secure DevSecOps practices, with a track record of building scalable, compliant solutions.

You will design, develop and oversee tests, audits and deployments, mentor teams of developers, and collaborate with product owners and scrum masters.

Qualifications

• Bachelor's degree in IT, Engineering, Mathematics, Business Administration or Innovation.
• 15+ years of software development experience.
• 15+ years of software engineering principles and SDLC.
• Backend development with Java/JavaScript/TypeScript/Node.js (10+ years).
• 10+ years building blockchain smart contracts on EVM networks.
• 10+ years blockchain security and audit prep.
• 5+ years Ethereum smart contract development.
• 5+ years Solidity, EVM, proxy patterns, gas optimisation, RBAC.
• 5+ years Hyperledger Besu network engineering.
• 5+ years Besu validator networks.
• 5+ years blockchain identity and tokenisation.
• 7+ years blockchain standards incl ERCs, EIP-712, EIP-1559, DIDs.
• 5+ years blockchain security, DevSecOps tooling.
• 5+ years Foundry, Hardhat, OpenZeppelin, Slither, Mythril, fuzz testing.
• 5+ years ethers.js, VIEM, Gnosis Safe, hardware wallets, EIP-712 signing.
• 5+ years GitLab CI/CD.
• 5+ years Puppet.
• APIs integration with smart contracts, wallets and dApps.
• Secure backend development: auth, authorization, input validation, logging.
• Unit/integration testing in CI/CD.
• Write clean, functional backend code and docs.
• Troubleshooting, performance and scalability.
• Experience managing teams of developers.
• English: min B2, strong communication.
• Certified Scrum Master.
• Certified Product Owner.

Connaissances

Blockchain development

Ethereum

Hyperledger Besu

Solidity

EVM

Smart contracts testing

Back-end development

SDLC

DevSecOps

API design

GitLab CI/CD

Security auditing

Team leadership

Scrum Master

Product Owner

English

Foundry

Hardhat

OpenZeppelin

Slither

Mythril

ETHERS.js

VIEM

Gnosis Safe

Formation

Bachelor's degree in IT/Engineering

Outils

Foundry

Hardhat

OpenZeppelin

Slither

Mythril

SWC Registry

OWASP

ethers.js

VIEM

Gnosis Safe

Description du poste

Language: English

Can work anywhere from the EU region, Occasional travel to Belgium will be required

Requirements

• Education: Bachelor's degree in IT, Engineering, Mathematics, Business Administration or Innovation.




• Software development experience: at least 15 years.




• Software engineering principles, modern web development practices and SDLC: at least 15 years.




• Back-end software development using Java, JavaScript, TypeScript and Node.js: at least 10 years.




• Design, development, testing and deployment of blockchain smart contracts on EVM-compatible networks: at least 10 years.




• Blockchain security, including smart contract testing, vulnerability assessment, secure development practices and audit preparation: at least 10 years.




• Ethereum smart contract development: at least 5 years.




• Solidity, EVM, upgradeable contracts, Contract Factory, Beacon Proxy, UUPS, Transparent Proxy, EIP-2535 Diamond Standard, gas optimisation, storage layout and RBAC: at least 5 years.




• Hyperledger Besu network engineering, including deployment, configuration, operation and maintenance of permissioned blockchain networks: at least 5 years.




• Hyperledger Besu, QBFT, IBFT2, live network upgrades, Genesis configuration, hard forks, troubleshooting and forensic diagnosis: at least 5 years.




• Experience as a validator coordinator or blockchain infrastructure engineer responsible for Hyperledger Besu validator networks: at least 5 years.




• Blockchain-based digital identity and tokenisation solutions: at least 5 years.




• Blockchain standards, digital identity and tokenisation technologies, including ERC-20, ERC-721, ERC-1155, ERC-1167, EIP-712, EIP-1559, DIDs, Verifiable Credentials and tokenisation: at least 7 years.




• Blockchain security, development and DevSecOps tooling: at least 5 years.




• Experience with Foundry, Hardhat, OpenZeppelin, Slither, Mythril, fuzz testing, SWC Registry, OWASP Smart Contract Top 10 and smart contract audit preparation: at least 5 years.




• Experience with ethers.js, VIEM, Gnosis Safe, hardware wallets, EIP-712 signing, ECDSA and key management: at least 5 years.




• GitLab CI/CD experience: at least 5 years.




• Experience with Puppet: at least 5 years.




• Ability to design and develop APIs and integrate smart contracts with backend services, wallets and dApps.




• Experience with secure backend development, including authentication, authorisation, input validation, secure storage, compliant logging and monitoring.




• Experience with unit and integration testing and integrating tests into CI/CD pipelines.




• Ability to write clean, functional backend code and technical documentation.




• Experience in troubleshooting, debugging and optimising applications for performance and scalability.




• Experience in managing teams of developers.




• English: minimum B2 level, with strong written and oral communication skills.




• Certified Scrum Master or equivalent Scrum Master certification.




• Certified Product Owner or equivalent Product Owner certification.

Nice to have

• Experience with AI-assisted software development tools, e.g. Claude Code.




• Previous experience in EU institutions or European Commission projects.