Toggle AI is seeking a Senior Machine Learning and AI Engineer to build and evolve AI systems for investment insights. This role involves designing, fine-tuning, and deploying ML and LLM-driven systems in production, integrating various AI models, and working with backend engineers to productionize solutions. The ideal candidate will have 5+ years of experience in building production ML/AI systems, strong Python skills, and an interest in fintech.
About the role
You have built real AI systems that ship, break, and get fixed under pressure. You care less about model demos and more about decisions that move capital. You want your work used daily by professional investors, not buried in notebooks. You are comfortable owning hard problems end to end. If you want a calm job optimizing benchmarks, this is not it. The Role, In Plain English You will build and evolve the AI systems that power Reflexivity's investment insights. This role exists because off-the-shelf models and generic pipelines are not enough. You will work at the intersection of reasoning engines, proprietary data, and real market impact. Your work directly affects how investors understand earnings, risk, and market catalysts. What You'll Be Responsible For Design, fine-tune, and deploy ML and LLM-driven systems used in production by professional investors Build and maintain inference pipelines that are fast, observable, and reliable Integrate OpenAI, Gemini, and Anthropic models into reasoning and knowledge systems Work closely with backend engineers to productionize models in Golang-based services Improve signal quality, not just model accuracy Review code and designs with a bias toward long-term maintainability What "Good" Looks Like in This Role After 3 months: You understand the product, data flows, and investor use cases deeply. You ship meaningful improvements. After 6 months: You own major parts of the AI stack. Your work improves insight quality and latency measurably. After 12 months: You are a technical reference point for AI decisions. You raise the bar for how AI is built at Reflexivity. Who You Are (Must-Haves) 5 plus years building ML or applied AI systems in production Startup experience working on a core product, not a side project Strong Python skills and experience integrating with backend systems Hands-on experience with AI-assisted coding tools like Cursor or Claude Code Fintech experience or strong personal investment background Comfortable owning outcomes, not just tasks Nice-to-Haves (Not Deal Breakers) Experience with LLM reasoning systems or knowledge graphs Exposure to Golang-based ML integrations Prior experience supporting investor-facing products How We Work In-office team with high trust and high ownership Direct communication, minimal process, strong opinions backed by data Engineers are expected to think about product impact, not just code We move fast when it matters and slow down when correctness matters more Why This Role Is Worth Your Time Direct influence on how professional investors make decisions Hard problems at the edge of AI, data, and finance Real ownership and technical autonomy Senior peers who care about quality and outcomes Compensation & Practicalities Base salary: £90,000 to £160,000 depending on experience Equity included In-office role based in London No agency candidates