Senior Full-Stack Software Engineer (Annual salary up to £95K) in London

Nyxium is a London-based deep tech company backed by top-tier investors. We are building an agentic AI and geospatial intelligence platform that supports siting, permitting, impact assessment, and decision-making for complex infrastructure projects, including energy systems, data centers, and other critical infrastructure.

Location: London

Right to work in the UK required (visa sponsorship considered on a case-by-case basis)

Time Commitment & Working Arrangement: This is a full-time position (40 hours per week). The role requires focused, dedicated commitment to Nyxium. External paid work, consulting, or freelance engagements outside Nyxium are not permitted during employment. Any academic affiliations, advisory roles, or unpaid activities must be disclosed and must not conflict with Nyxium’s work, priorities, or intellectual property. We value sustainable working practices and do not expect routine overtime, but we do expect full professional focus during agreed working hours.

Role Summary: We are hiring a Senior Full-Stack Software Engineer (AI / ML) to build and own Nyxium’s core application and ML integration layer. This role sits between:

• AI and ML systems (LLMs, NLP pipelines, decision logic)
• Backend services and APIs
• Data and document workflows
• User-facing analytical and operational tooling

You will work directly with the founders and the Geospatial AI Engineer to turn advanced AI and spatial intelligence into robust, production-grade software that real teams depend on. This is a senior individual contributor role with strong architectural ownership.

Key Responsibilities:

• AI-Enabled Backend Systems: Design and build backend services that integrate AI and ML workflows into production systems. Develop APIs and orchestration layers. Ensure AI outputs are traceable, explainable, and suitable for audit and regulatory review. Develop Retrieval-Augmented Generation (RAG) and LLM-based pipelines for data imputation, NLP analysis, and decision support. Build systems that process, normalize, classify, and enrich large volumes of structured and unstructured documents. Regulatory documentation compliance evidence tracking. Developer and user automation. Design pipelines that balance ML-driven inference with deterministic rules and safeguards.
• Full-Stack Application Development: Build and maintain user-facing applications that expose complex AI outputs in clear, actionable ways. Implement interactive dashboards, workflow UIs, and operational tools. Collaborate on frontend architecture using modern frameworks (React / Next.js), with a focus on correctness and clarity rather than visual novelty. Design schemas and APIs for systems that combine regulatory and temporal data. Work with Postgres (PostGIS a plus), MongoDB, and analytical data stores. Build reliable async processing, background jobs, and batch pipelines.
• Production Quality & Developer Experience: Improve system reliability, testing coverage, and observability. Contribute to CI/CD pipelines and deployment workflows. Raise internal standards for code quality, documentation, and maintainability. Build systems that other engineers and stakeholders can confidently rely on. Work closely with founders on roadmap execution and technical trade-offs. Collaborate daily with the Geospatial AI Engineer to integrate spatial intelligence into the platform. Take full ownership of major system components from design through deployment. Contribute to technical decision-making as the platform scales.

Required Qualifications:

• Education: Bachelor’s or master’s degree in computer science, Data Science, Engineering, or a closely related field. Equivalent industry experience considered.
• Core Technical Skills: Strong Python experience in production systems. Experience with FastAPI, Flask, or similar frameworks. Experience building ML-backed APIs and services.
• AI / ML Integration: Hands-on experience integrating ML or LLM systems into real applications. Familiarity with NLP pipelines, document processing, or AI workflows. Understanding of model lifecycle concerns such as versioning, latency, and reliability.
• Data & Platforms: Experience with SQL and NoSQL databases. Schema design for complex, evolving data models. Experience with background jobs, async workflows, and data pipelines.
• Frontend (Applied): Working knowledge of React and modern frontend patterns. Experience building dashboards or analytical user interfaces. Experience deploying systems on AWS and/or GCP. Familiarity with Docker, CI/CD, and production monitoring.
• Experience: 5+ years of professional experience in software engineering, data engineering, or ML-enabled systems. 5+ years of experience in geospatial analytics, applied ML and computer vision, including production systems. Demonstrated experience delivering end-to-end ML solutions in complex, real-world environments. Proven experience shipping production systems used by real users. Comfortable operating in early-stage or high-ownership environments.

Preferred / Nice-to-Have:

• Experience with geospatial data or spatial platforms.
• Experience in environmental, infrastructure, healthcare, or regulated domains.
• Experience building internal tools, developer platforms, or workflow automation systems.
• Background in developer experience or platform engineering.

What Success Looks Like: You ship reliable, production-grade systems that form the backbone of the platform. AI and ML capabilities are usable, trustworthy, and well-integrated. Developers and users experience clear, stable workflows instead of brittle tools. You raise the overall engineering bar through thoughtful system design and execution.

Compensation: We offer above market, competitive salary (Up to £95,000 annual) and meaningful equity. Final offer depends on experience and scope of responsibility. Flexible, remote-first working arrangement. Pension contributions (UK auto-enrolment). Paid annual leave and UK public holidays. Direct access to founders and real influence over technical direction. Opportunity to work on high-impact, technically challenging problems from the ground up.

Why Join Us: You will build core systems, not surface features. Your work will directly shape a category-defining platform. You will operate in a small, senior, high-trust technical team. You will work on problems that matter in real regulatory and infrastructure contexts.