Jim Posen
Co-Founder & CTO at Irreducible
Berlin, Germany
Summary
🤩
Rockstar🎓
Top SchoolJim Posen is a co-founder and CTO with 14 years of engineering experience building high-performance, cryptography-focused systems from embedded firmware to blockchain infrastructure. Based in Berlin, he leads an FPGA-accelerated zk-SNARK proof stack at Irreducible, combining hardware, Rust, and cryptographic engineering to dramatically speed zero-knowledge proof generation. A long-time contributor to flagship cryptocurrency projects (Bitcoin Core, Bitcoin-ABC, Peercoin, Parity/Substrate), Jim specializes in backend systems, database and index refactors, and protocol-level optimizations that improve performance and maintainability. His background includes leading payments backend and transaction processing at Coinbase, firmware reverse-engineering and secure integration work at Red Balloon Security, and core networking and consensus fixes for Ethereum clients. Colleagues know him for pragmatic, reusable refactors—“the truth is in the code”—and for surfacing subtle correctness and efficiency wins (e.g., block-filter and index improvements, XOR-distance bug fixes) that pay dividends in production.
14 years of coding experience
8 years of employment as a software developer
BSE Electrical and Computer Engineering Computer Science, BSE Electrical and Computer Engineering Computer Science at Duke UniversityStuyvesant High SchoolMaster's degree Computer Science, Master's degree Computer Science at Stanford University
Github Skills (46)
substrate10
c-language10
memory-management10
databases10
bitcoin10
leveldb10
data-serialization10
bitcoins10
rust-wasm10
indexing10
data-structure10
kademlia10
serialization10
cryptocurrency10
gas-optimization10
Programming languages (16)
Github contributions (5)
peercoin/peercoin
May 2018 - May 2020
Reference implementation of the Peercoin protocol.
Role in this project:
Back-end Developer
Back-end DeveloperContributions:50 commits in 2 years
Contributions summary:Jim's contributions primarily involve the refactoring and optimization of database-related code within the Peercoin project. They removed obsolete methods, made reusable base classes for index databases, extracted logic into reusable base classes, and implemented an index for block filters. The user's work also included improving code performance, pre-allocating disk space, and handling the correct signal service bits. The changes aim to improve performance, efficiency, and maintainability.
proof-of-stakeblockchaindecentralizedminablecryptocurrency
bitcoin/bitcoin
May 2018 - May 2020
Bitcoin Core integration/staging tree
Role in this project:Back-end Developer
Back-end DeveloperContributions:51 commits, 27 PRs, 428 comments in 2 years
Contributions summary:Jim primarily contributed to the Bitcoin Core codebase by modifying database-related code. Their work included removing obsolete methods from the `CBlockTreeDB`, creating a reusable base class for index databases, and refactoring the transaction index logic. They also improved the code by extracting logic from `TxIndex` into a reusable base class and ensuring proper handling of block filter indexes.
cryptographyp2pc-plus-pluscryptocurrencybitcoin-core
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