Senior Blockchain Developer

About the Role

We are looking for an experienced Senior Blockchain Developer with deep expertise in the Bitcoin protocol to join a long-term project building institutional-grade Bitcoin wallet and custody infrastructure.

This is not a general blockchain role. We’re looking for engineers with real production experience working with Bitcoin, including transaction construction, UTXO management, multi-signature workflows, fee optimization, and wallet infrastructure at scale.

What You’ll Do

• Design and develop secure Bitcoin wallet infrastructure
• Build and maintain transaction construction and signing workflows (PSBT, SegWit)
• Implement UTXO management, balance tracking, and wallet recovery mechanisms
• Develop multi-signature coordination and signing flows
• Optimize transaction fee estimation and fee bumping strategies (RBF, CPFP)
• Monitor transaction lifecycle and implement remediation strategies for unconfirmed transactions
• Develop backend services using Java and Spring Boot
• Collaborate across engineering teams within a shared monorepo environment
• Contribute to architecture, code reviews, and technical discussions
• Write high-quality, well-tested code using TDD/BDD practices

Requirements

Must Have

• 3+ years of production experience developing Bitcoin-based applications
• Strong commercial Java experience
• Experience with Spring Boot
• Strong SQL knowledge
• Deep understanding of the Bitcoin protocol, including:
  • PSBT (BIP-174)
  • UTXO management
  • Coin selection algorithms
  • SegWit transactions
  • Bitcoin descriptors
• Experience implementing multi-signature wallets:
  • BIP-48
  • BIP-67
  • P2WSH
• Experience with:
  • Fee estimation
  • RBF
  • CPFP
  • Mempool monitoring
• Experience constructing Bitcoin transactions, including:
  • Witness data
  • BIP-143
  • DER signatures
  • SIGHASH types
• Experience managing:
  • HD wallets
  • Gap limits
  • Address derivation
  • Address discovery
• Strong understanding of Bitcoin transaction lifecycle and network behavior
• Experience operating production Bitcoin custody or wallet infrastructure
• Familiarity with:
  • Domain-Driven Design (DDD)
  • TDD and/or BDD
  • Monorepo development
  • CI/CD workflows
• Strong communication skills in English

Nice to Have

• Experience with additional blockchain protocols
• Institutional custody platform experience
• Experience building highly available financial systems
• Strong software architecture background

What We’re Looking For

• Deep Bitcoin protocol expertise
• Strong ownership mindset
• Excellent debugging and problem-solving skills
• Comfortable working in collaborative engineering environments
• Ability to communicate technical decisions clearly
• Passion for secure, high-quality software