Senior Bitcoin / Blockchain Engineer (Java)

Job description

PioGroup Software is a team of professionals passionate about building reliable digital products. We are looking for an experienced Senior Blockchain Engineer with strong production experience working with the Bitcoin protocol and Bitcoin wallet/custody infrastructure.

The main focus of the role is developing and maintaining Bitcoin wallet infrastructure, including UTXO management, transaction construction and signing, PSBT, SegWit, multi-signature flows, fee management, and transaction lifecycle handling.

For this position, hands-on production experience specifically with the Bitcoin protocol is essential. General blockchain or Web3 experience alone is not sufficient.

Requirements

- 3+ years of production experience with Bitcoin / BTC infrastructure.

- Hands-on experience with Bitcoin-based protocols, UTXO model, PSBT, and BIP standards.

- Strong experience with Java, Spring Boot, and SQL.

- Experience working with production wallet or custody infrastructure.

- Good understanding of TDD and/or BDD practices.

- Familiarity with Domain-Driven Design principles.

- Experience working in a monorepo environment with shared libraries and coordinated CI/CD pipelines.

- Professional written and spoken English.

- Proactive communication and ability to raise blockers, technical concerns, and cross-team dependencies.

Bitcoin Protocol Expertise

We expect strong practical knowledge of:

- PSBT and BIP-174.

- UTXO management and coin selection.

- SegWit transaction structures.

- Bitcoin script types and descriptor formats.

- HD wallets and derivation paths.

- BIP-48 and BIP-67.

- P2WSH and multi-signature transaction flows.

- PSBT combination, signing, and finalisation.

- Witness data and BIP-143.

- DER signature encoding, low-S enforcement, and sighash types.

- UTXO indexing and balance calculation.

- Address discovery, gap limits, change address allocation, and address reuse prevention.

Transaction Lifecycle & Fee Management

Production experience with:

- Mempool monitoring.

- Fee estimation and fee-rate prediction.

- RBF (Replace-By-Fee).

- CPFP (Child-Pays-For-Parent).

- Stuck transaction detection.

- Transaction replacement and rebroadcasting.

- Confirmation monitoring.

- Double-spend detection.

- UTXO consolidation during low-fee periods.

Candidates should also clearly understand the operational difference between a transaction being:

- Broadcast.

- Accepted into the mempool.

- Confirmed.

- Confirmed at depth N.

A strong understanding of Bitcoin probabilistic finality, dust limits, fee spikes during network congestion, and the behaviour of unconfirmed transactions is also required.

Responsibilities

- Develop and maintain Bitcoin wallet infrastructure.

- Manage UTXOs and wallet balances.

- Construct Bitcoin transactions.

- Work with PSBT and SegWit.

- Implement multi-signature transaction flows.

- Handle fee estimation and fee bumping using RBF and CPFP.

- Monitor mempool activity and transaction lifecycle.

- Implement deposit detection and address-level balance monitoring.

- Support wallet recovery and descriptor-based address discovery.

- Participate in technical design and architecture decisions.

- Collaborate with other engineering squads and shared platform components.

Nice to Have

- Experience with multiple blockchain protocols.

- Experience with institutional-grade custody or wallet platforms.

- Experience working with systems processing high volumes of Bitcoin transactions.

Important: we are specifically looking for candidates with documented commercial experience working with the Bitcoin protocol, including UTXO management, PSBT, SegWit, BIP standards, and the Bitcoin transaction lifecycle. Testnet-only, personal wallet, or exclusively Ethereum/Web3 experience will not be sufficient for this role.