We are looking for a creative problem-solver to join our development team. This is a mid-level to senior position where you will have a direct impact as we develop new modeling capabilities to enhance GoldSim, our state-of-the-art modeling and simulation framework. What you'll Do Numerical & Algorithmic Ownership • Own the numerical solutions and mathematical/computer science algorithms underlying GoldSim's simulation engine - from the theoretical foundation (equations, algorithm design) through to implementation in our C++ codebase. • Push practical, real-world improvements to GoldSim's numerical capabilities, and propose new features driven by everyday or discipline-specific customer needs. • Participate in design discussions across the full development lifecycle, not just the mathematical layer. Model Building & Verification • Build GoldSim models that apply and exercise the platform's numerical capabilities - for QA and verification, as example models shipped with the product, and in direct support of customers. • Use hands-on model-building as a primary way to validate that new or improved algorithms behave correctly in practice. Documentation & Knowledge Transfer • Document both the theoretical basis (equations, algorithm descriptions) and the practical implementation of GoldSim's numerical methods, so this knowledge isn't concentrated in one person. • Partner with the founding engineer to formalize existing modeling, QA, and support methodology. Collaboration & Support • Work alongside the software engineering team to integrate new or improved numerical capabilities into the broader platform. • Translate business and product requirements into technical specifications. • Serve as a technical resource for customer support and QA on advanced modeling and numerical questions. • Communicate technical/mathematical concepts clearly to engineers, QA, and product stakeholders. Growth & Modernization • Bring curiosity for modern computational approaches - including applying machine learning to accelerate, approximate, or extend traditional numerical simulation methods. • Help identify opportunities to modernize GoldSim's existing algorithmic infrastructure. Requirements • Masters or PhD level in science or engineering, with outstanding academic performance. • Broad experience with applied math and numerical methods for solving science and engineering problems (e.g., matrix algebra, numerical methods for solving partial differential equations). • Earth sciences or civil engineering background, preferably including contaminant transport modeling. • Extensive C++ programming experience, ideally in scientific or engineering applications; familiarity with commercial or open-source numerical libraries and frameworks is a plus. • Proven ability to design and implement practical numerical solutions to real-world problems. • Good communications skills, must write effectively and enjoy interacting with other team members. • Experience developing and supporting Windows desktop applications is a plus, as is hands-on experience with data science tools such as MATLAB, R, or Tableau. • Experience applying AI/ML techniques (e.g., machine learning models, LLM-based tools, or AI-assisted development) to scientific or engineering software is a plus. Why GoldSim Join a team where your work directly shapes software that engineers and scientists rely on around the world. You'll take on meaningful technical challenges, enjoy real autonomy, and help define the future of a product with a global reputation for excellence. We have offices across the US where you have the opportunity to come in as you would like including one in Seattle.