Job Title

At Nucleus, we’re building AI systems that become most powerful when others can build on top of them. Our APIs are not just interfaces - they are the foundation that lets developers, partners, and enterprises bring advanced intelligence into real products and workflows.We’re hiring an API Engineer to design, build, and maintain the public and partner APIs that expose Nucleus models, services, and platform capabilities to the outside world. This is a high-impact backend role focused on creating reliable, secure, and developer-friendly interfaces that make our technology usable at scale.About the roleAs an API Engineer at Nucleus, you will own core API surfaces that connect external developers and enterprise customers to our models and platform systems. You’ll work on everything from API design and service implementation to authentication, rate limiting, versioning, observability, and reliability.This role sits at the intersection of platform engineering, product, and developer experience. You’ll collaborate closely with product, frontend, infrastructure, solutions, and AI teams to ensure our APIs are elegant to use, robust in production, and capable of supporting a wide range of customer needs.What you’ll doDesign, build, and maintain public and partner-facing APIs that expose Nucleus models, workflows, and platform capabilities.Develop backend services and interface layers that are reliable, scalable, secure, and easy for developers to integrate.Define clean API contracts, data models, and versioning strategies that support long-term platform evolution.Build systems for authentication, authorization, rate limiting, usage tracking, and access control across external API surfaces.Improve API reliability, latency, and observability through strong engineering practices, testing, and production monitoring.Partner with product and developer-facing teams to create APIs that are intuitive, well-structured, and aligned with real user needs.Collaborate with infrastructure and security teams to ensure enterprise-grade standards for resilience, compliance, and safe access.Contribute to API documentation, tooling, and internal platform abstractions that improve developer experience and accelerate integration.What we’re looking forStrong backend engineering experience with languages such as Python, Go, Java, or Node.js/TypeScript.Experience designing and operating production APIs used by external developers, partners, or enterprise customers.Solid understanding of RESTful API design, service architecture, schema design, authentication, authorization, and versioning.Familiarity with API infrastructure concerns such as rate limiting, quotas, retries, error handling, idempotency, and observability.Experience with cloud platforms and modern engineering tools such as AWS/GCP/Azure, Docker, CI/CD, logging, and monitoring.Good judgment around security, reliability, and backward compatibility for externally facing systems.Strong collaboration and communication skills, especially when working across product, infrastructure, and customer-facing teams.A thoughtful approach to developer experience and a clear understanding of what makes APIs simple, powerful, and trustworthy.What makes Nucleus differentNucleus is building intelligent systems for real-world use at meaningful scale. To do that well, we need APIs that do more than function — they need to be dependable, expressive, and carefully designed so developers and enterprises can confidently build on them.In this role, you’ll help define how the outside world experiences Nucleus technically. Your work will shape the interfaces through which our models become products, integrations, and critical business capabilities. If you care deeply about backend systems, developer platforms, and building excellent APIs for the future of AI, we’d love to hear from you.