Senior Software Engineer (AI Engineer)

At Fluxon, we believe that how you build matters as much as what you build. We help businesses navigate their most important technology decisions with confidence, and take responsibility for seeing them through. Founded by ex-Googlers and startup veterans, we’re proud to partner with teams behind some of the most ambitious products, including Google, OpenAI, Anthropic, Walmart and Stripe. 

Our work spans strategy, design, and engineering — often in complex, AI-driven environments — where clarity, speed and quality are the standard. We use AI intentionally, applying it only where it adds real value and expands what’s possible. Care shapes everything we do.

Inside Fluxon, you’ll find a global, remote-first team of experienced builders, who are curious, kind and serious about their craft. We’re building a place where people can take ownership, solve problems that matter and do work they’re proud to stand behind. If you want to do your best work alongside people who care as much as you do, you’ll feel at home here.

The role is open to candidates preferably based in Lisbon, Portugal.

As an AI Engineer at Fluxon, you’ll take the lead in designing, building and deploying AI-powered applications for our clients.

You'll be responsible for:

• System Architecture: Design and implement end-to-end AI systems and their parts, including data ingestion, preprocessing, model inference, and output structuring
• Generative AI Development: Build and optimize RAG (Retrieval-Augmented Generation) systems and Agentic workflows using frameworks like LangChain, LangGraph, ADK (Agent Development Kit), Genkit
• Production Engineering: Deploy models to production environments (AWS/GCP/Azure) using Docker and Kubernetes, ensuring high availability and scalability
• Evaluation & Monitoring: Implement feedback loops to evaluate model performance (accuracy, hallucinations, relevance) and set up monitoring for drift in production
• Collaboration: Work closely with other engineers to integrate AI endpoints into the core product and with product managers to define AI capabilities
• Model Optimization: Fine-tune open-source models (e.g., Llama, Mistral) for specific domain tasks and optimize them for latency and cost

You'll work with technologies including:

Languages

• Python (Preferred)
• Java / C++ / Scala / R / JavaScript   

AI / ML

• LangChain
• LangGraph
• Google ADK
• Genkit
• OpenAI API
• LLM - Large Language Model
• Vertex AI

Cloud & Infrastructure

• Platforms: Google Cloud Platform (GCP) or Amazon Web Services (AWS)
• Storage: Google Cloud Storage (GCS) or AWS S3
• Orchestration: Temporal, Kubernetes

Data Stores

• PostgreSQL
• Firestore
• MongoDB

Monitoring & Observability

• GCP Cloud Monitoring Suite

• 5+ years of industry experience in software engineering roles
• Strong proficiency in Python or any preferred AI programming language such as Scala, Javascript and Java
• Strong understanding of Transformer architectures, embeddings, and vector similarity search
• Experience integrating with LLM provider APIs (OpenAI, Anthropic, Google Vertex AI)
• Hands-on experience with agent workflows like LangChain, LangGraph
• Experience with Vector Databases and traditional SQL / NoSQL databases
• Familiarity with cloud platforms, preferably GCP or AWS
• Understanding of patterns like RAG (Retrieval-Augmented Generation), few-shot prompting, and Fine-Tuning
• Solid understanding of software development practices including version control (Git) and CI/CD

• Experience with Google Cloud Platform (GCP) services, specifically Vertex AI, Firestore, and Cloud Functions
• Knowledge of prompt engineering techniques (Chain-of-Thought, ReAct, Tree of Thoughts)
• Experience building "Agentic" workflows where AI can execute tools or API calls autonomously