Software Library Engineer (C++)

Blockstream was founded in 2014 by Dr. Adam Back and a group of fellow cryptographers and engineers passionate about Bitcoin and its potential to change the future of finance. Focusing on building fundamental Bitcoin infrastructure, Blockstream quickly grew into one of the leading technology power houses of the industry.

At Blockstream, we’re building solutions on Bitcoin that will disrupt the existing financial system. We imagine a world where individuals and businesses can easily access a global, permissionless system to secure their money, use it every day, and invest it or put it to work. In pursuit of our expansive vision, we’ve built a full stack of innovative products on top of the Bitcoin protocol, from layer 2 projects like Liquid and Core Lightning, to end user software and hardware wallets like Green and Jade. Our brand stands for innovation in the Bitcoin community, and we’re growing our team to accelerate the future. Come join us in our mission!

We are seeking an experienced Software Library Engineer, with deep expertise in C++ to lead the development and maintenance of the Green Development Kit (GDK), a vital software development kit for our bitcoin wallet apps. This role focuses on the Core SDK (written in C/C++) while overseeing its integration with Rust modules, language wrappers (Java, Python, Swift), build systems (CMake, scripts, Docker), testing frameworks, and documentation. The ideal candidate will combine strong technical skills with a collaborative mindset to ensure the project remains robust, efficient, and developer-friendly.

What You’ll Be Doing (Responsibilities):

• Core SDK Development & Wrapper Integration (C/C++)
  • Lead the development, maintenance and testing of the Core SDK, written in C/C++.
  • Debug complex issues, enhance performance, and ensure seamless integration with the Blockstream wallets and third party users
• Build System Contributions
  • Maintain and enhance CMake build files, build scripts, and Docker configurations to support C++ development and cross-component builds.
  • Resolve build-related issues and optimize for multiple platforms.
  • Publish regular releases incorporating new features, fixes and performance improvements
• Testing & Continuous Integration (CI)
• Develop and maintain C++-focused test cases within the testing suite.
• Work with CI pipelines to validate Core SDK changes and their impact on downstream components.
• Documentation
• Document C++ APIs, core functionality, and integration points for contributors and end-users.
• Collaborate with the team to keep project-wide documentation current and accessible.
• Collaboration with Mobile App Developers
• Partner with mobile app developers, the primary users of the GDK library, to understand their needs and ensure the Core SDK meets requirements for iOS (Swift) and Android (Kotlin) environments.
• Provide technical support and guidance to app developers integrating the library into their applications.

What We Look For In You (Required Qualifications):

• Experience:
• 5+ years of software development experience, with at least 3 years focused on C++ in complex, multi-component systems.
• Experience with cross-language integration (e.g., C++ with Rust, Python, Java, or Swift).
• Familiarity with CMake, Docker, and CI/CD workflows.
• Technical Skills:
• Expert-level proficiency in C++ (modern standards, e.g., C++17/20).
• Strong understanding of systems programming, memory management, and performance optimization.
• Knowledge of testing frameworks and writing robust unit/integration tests.
• Soft Skills:
• Exceptional problem-solving and debugging capabilities.
• Clear communication skills for documenting code and collaborating with distributed teams.
• Ability to manage priorities and lead technical initiatives.

Nice To Haves (Preferred Qualifications):

• Experience with Rust and/or Python.
• Background in bitcoin or cryptocurrency development.
• Knowledge of cryptography.
• Familiarity with SWIG or similar tools for language bindings.
• Contributions to open-source projects on GitHub, especially in C++ ecosystems.
• Bachelor’s degree in Computer Science, Engineering, or a related field (or equivalent experience).