Senior Full-Stack Engineer (Python + React)

Architus specialises in connecting leading Fintech companies with top EU engineering talent, helping to build high-performing technology teams and establish a presence overseas. With offices in London, Vilnius and Kaunas, Architus has a strong track-record and impressive list of clients such as Invesco, Tide, Capital Group, Schroders, BNP Paribas, and HSBC. The Opportunity Architus is partnering with a leading company in AI-powered anti-money laundering and fraud detection. With over $100m in funding and clients including tier-1 banks, the company is growing fast and expanding internationally from its EU-based headquarters. Trusted by banks and payment providers worldwide, this organization combines traditional rules with explainable AI to detect financial crime more effectively while improving efficiency and reducing false positives. As a Senior Full Stack Engineer at Hawk, your mission is to build the engine and the experience for their agentic AI Investigation Agent — a new product that fundamentally rethinks how human analysts collaborate with autonomous AI to investigate financial crime. You will own features end-to-end: from the LangGraph workflow that drives the agent's reasoning, through the FastAPI services and Postgres/Redis infrastructure that make it reliable at scale, all the way up to the React/shadcn UI that surfaces the agent's findings to analysts. This is a high-ownership role for someone who refuses to throw work over the wall — you ship the whole feature, and you ship it well. About the role Design, build, and operate the backend systems that power the Investigation Agent: LangGraph workflows, FastAPI services, Postgres and Redis data layers, Kubernetes deployments, and Langfuse-based observability and evaluation. Build the frontend surface that makes the agent's work legible: React + TypeScript components in shadcn/ui that surface agent reasoning, evidence, and explainability so analysts can trust, challenge, or take over. Own features end-to-end. You take a problem from spec to production — backend, frontend, infra, observability, evals — without waiting for someone else to finish their part first. Make the agent reliable. Build the eval harnesses, tracing, and feedback loops in Langfuse that turn "the model usually does the right thing" into "the model demonstrably does the right thing, and we know when it doesn't." Partner closely with Product/UX, Data Science, and the rest of Engineering to shape what gets built — not just how. You question the "why" behind features and push back when something doesn't feel right. Champion an AI-native engineering workflow. You use Claude Code, Cursor, or equivalent agentic coding tools as a daily part of how you work, and you help raise the bar for how the team uses them. If you find yourself doing the same thing twice, your natural instinct is to automate it. Help establish engineering best practices for agentic products at Hawk: how we test agents, how we deploy them, how we monitor them, how we roll back when they misbehave. What we are looking for Core Backend Expertise: Strong hands-on experience with Python, FastAPI, Postgres, and Redis, with a track record of building robust, scalable backend architectures. Strong Frontend Chops & UI Intuition: Advanced skills in React, TypeScript, and modern component libraries (shadcn/ui, Material UI). Strong UX/UI design intuition with the ability to independently build clean, highly performant, and user-centric interfaces. Genuinely Full-Stack Mindset: An end-to-end feature ownership approach rather than a strict separation between backend and frontend roles—taking ownership from API architecture to final UI execution. Cloud & Infrastructure: Proven proficiency in deploying, managing, and operating services on Kubernetes within AWS environments. Performance & Diagnostics: Practical experience with latency monitoring, diagnostics, and system optimization, combined with a deep understanding of writing high-availability code designed to perform under heavy production load. Hands-on AI Workflow: Fluency with agentic coding tools (Claude Code, Cursor, or equivalent) as a core part of the daily workflow, with a clear understanding of their strengths, limitations, and optimal application. Product & Systems Thinking: Excellent holistic thinking and problem-solving skills, with a drive to shape the product direction rather than simply executing pre-defined tickets. Collaborative Communication: Excellent communication skills and a collaborative mindset, capable of clearly articulating technical trade-offs to both technical and non-technical stakeholders. Nice to have Production experience with LangGraph (or equivalent agent orchestration frameworks) and Langfuse (or equivalent LLM observability/eval tooling). Prior experience in Anti-Financial Crime (AML, fraud, compliance, or investigations tooling) — or a deep curiosity to go learn the domain fast. What you’ll get in return Salary: Starting from €6,000 gross/month , depending on your experience (full-time only). Career Growth: Accelerate your professional journey by working with cutting-edge technologies in a truly global environment. Holidays: Enjoy extra vacation days to recharge and unwind. Flexibility: Benefit from hybrid working options for a healthy work-life balance. Workplace: A modern, pet-friendly office equipped with parking and plenty of snacks to keep you fueled and productive. High-Spec Hardware: Brand-new, high-performance equipment provided to support your work from day one. Team Environment: A dynamic, collaborative, and friendly working atmosphere. Perks: Stay balanced with our wellness program, enjoy additional health insurance, plan for the future with 3rd-pillar pension benefits, and perform at your best with high-spec hardware. Ready to Join Us? If you’re enthusiastic about this opportunity and believe you’re the right fit, we’d love to hear from you! Apply now and let’s create something amazing together. We look forward to meeting the next Architus star!