Mobile Engineer
Castle Island Ventures is a venture capital firm focused exclusively on public blockchains, investing in early-stage companies at the intersection of traditional finance and public blockchains.
About Castle Island Ventures
Castle Island Ventures is a venture capital firm focused exclusively on public blockchains. Their mission is to support entrepreneurs building the infrastructure and application companies required to help transformative blockchain protocols reach their full potential. They describe their focus as 'accelerating frictionless finance,' investing in early-stage companies operating at the intersection of traditional finance and public blockchains. The firm also produces a podcast and newsletter covering topics in this space, and maintains a portfolio of companies whose open roles are listed on their jobs board.
Skills
About the Role
You will design and implement high-quality native mobile SDKs that enable developers to integrate embedded wallet functionality into their applications, with a strong focus on API ergonomics, performance, and reliability. You'll own SDK features end-to-end, from API design and architecture through implementation, testing, release, versioning, and developer documentation. You'll build and maintain secure, reliable SDK components for wallet operations, including cryptographic operations, blockchain interactions, and security-sensitive flows. You'll define and evolve the SDK architecture to support long-term maintainability, backward compatibility, and adoption across diverse customer applications. You'll also build sample applications and demos, create clear documentation, and work closely with developer relations and support teams to help customers succeed. You'll help raise the bar for quality and operational excellence around testing, observability, releases, and code health, while contributing to a culture of ownership through hands-on work, code reviews, and knowledge sharing.
Requirements
- 5+ years of software engineering experience with deep focus on mobile development and shipping production-grade SDKs
- Demonstrated track record of building and shipping high-quality code
- Strong hands-on experience with iOS (Swift) and/or Android (Kotlin); experience with React Native or other cross-platform frameworks
- Experience building mobile SDKs or shared libraries including API design, versioning, packaging, and long-term maintenance
- Experience with blockchain-enabled mobile systems including wallet flows, signing, and on-chain interactions
- Experience working on security-sensitive mobile software such as key management, secure storage, cryptography, or financial products
- Strong grasp of mobile engineering best practices including CI/CD, automated testing, release management, and observability
- Ability to independently own problems and deliver end-to-end solutions
- Comfortable making long-term architectural decisions while remaining pragmatic and adaptable
- B.Sc. in Computer Science / Engineering or equivalent practical experience
Responsibilities
- Design and implement native mobile SDKs for embedded wallet functionality
- Own SDK features end-to-end from API design through release and documentation
- Build and maintain secure SDK components for wallet operations including cryptographic operations and blockchain interactions
- Define and evolve SDK architecture for long-term maintainability and backward compatibility
- Build sample applications and demos showcasing SDK capabilities
- Create SDK documentation and integration guides
- Work with developer relations and support teams to address integration challenges
- Establish best practices around testing, observability, releases, and code health
- Contribute to a culture of ownership through code reviews and knowledge sharing