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