Senior AI Engineer (Backend-Focused)

About us: Talent has no borders. Proxify's mission is to connect top developers around the world with the opportunities they deserve. So, it doesn't matter where you are; we are here to help you fast-track your independent career in the right direction. 🙂 Since our launch, Proxify's developers have successfully worked with 1200+ happy clients to build their products and growth features. 5000+ talented developers trust Proxify and its network to fulfill their dreams and objectives. Proxify is shaped by a global network of supportive, talented developers interested in remote full-time jobs. Our Glassdoor (4.5/5) and Trustpilot (4.8/5) ratings reflect the trust developers place in us and our commitment to our members' success. The Role: We are looking for a Senior AI Engineer to join one of our high-growth client teams to lead the development of next-generation autonomous systems. This is a backend-heavy fullstack role where you will be responsible for more than just simple prompt engineering. You will be architecting Agentic Workflows—systems that can reason, use tools, and execute complex coding tasks autonomously. The ideal candidate is a language-agnostic engineer who is obsessed with the Claude ecosystem and has hands-on experience building systems where AI agents interact with real-world data and codebases. You will bridge the gap between advanced LLM capabilities and robust, scalable backend production environments. What we are looking for: Deep expertise in Agentic Development. You should be comfortable building multi-agent systems, ReAct loops, and self-correcting workflows. Mastery of the Claude 3/3.5 family. You understand how to leverage Claude’s high reasoning capabilities and long context windows for complex logic. Experience building "AI-coding" features—using LLMs to generate, refactor, and test code programmatically within an application. Strong proficiency in at least one major backend language (Python, C#, or JavaScript/Node.js) and the ability to design the infrastructure (APIs, Webhooks, Databases) that supports AI agents. While backend-heavy, you are comfortable building the necessary frontend components (React/Vue) to allow users to interact with AI agents seamlessly. Extensive experience giving LLMs "tools"—designing clean API interfaces that agents can call to perform actions in the physical or digital world. Intermediate-advanced English level. Time zone: CET (+/- 3 hours). We are unable to consider applications from candidates in other time zones. Nice-to-Have: Experience with LangChain, LangGraph, or CrewAI. Knowledge of Vector Databases (Pinecone, Weaviate) and advanced RAG patterns. Familiarity with LLM Observability tools (LangSmith, Helicone) to debug agentic reasoning chains. Background in Software Engineering Fundamentals: You treat AI code like production code (CI/CD, Unit Testing, Version Control). Responsibilities: Design and deploy autonomous agents that can handle end-to-end tasks, specifically focusing on Claude-based coding agents. Build the scalable "brains" of the application, ensuring that AI reasoning is integrated into the core business logic. Refine system prompts and multi-shot examples to maximize Claude’s reasoning performance. Implement guardrails and validation layers to ensure that agentic outputs are safe, predictable, and high-quality. Work with Product and UX teams to define how "AI Agents" should feel and behave within the product interface. What we offer: Get paid, not played No more unreliable clients. Enjoy on-time monthly payments with flexible withdrawal options. Predictable project hours Enjoy a harmonious work-life balance with consistent 8-hour working days with clients. Flex days, so you can recharge Enjoy up to 24 flex days off per year without losing pay, for full-time positions found through Proxify. Career-accelerating positions at cutting-edge companies Discover exclusive long-term remote positions at the world's most exciting companies. Hand-picked opportuni