Senior AI Engineer

Senior AI Engineer

About Sierra Studio

When you apply to Sierra, you join an ecosystem. We specialize in connecting talented Brazilian professionals with exciting career opportunities in a highly-vetted small community of growing companies in the US. Applying to Sierra seamlessly integrates you into this ecosystem, granting automatic eligibility for all relevant opportunities we offer.

About our hiring partner

Our hiring partner is a leader in payment orchestration, building the infrastructure that powers frictionless, global transactions for modern businesses. Their mission is to simplify and revolutionize how payments move — enabling merchants, consumers, and partners to operate with flexibility, intelligence, and trust. They're entering a new chapter: infusing artificial intelligence across their products and internal operations. They aim to design intelligent systems that create exponential efficiency, enhance user experiences, and unlock new sources of revenue.

Founded in 2021 by second-time founders who came from Rappi, a very successful startup in Latin America, our hiring partner identified a real business need that Rappi was facing - problems processing different types of payments across different markets. They realized this wasn't just a problem Rappi was experiencing, but a widespread issue affecting many merchants. Based on this real business need, they evolved the business to solve payment orchestration challenges for companies operating globally.

Today, our hiring partner has over 250 people and is currently a Series A startup moving to Series B by next year, with mass expansion in the plans. They are backed by different investors and VCs and are investing heavily in AI.

The Role

Our hiring partner is seeking a Senior AI Engineer to architect, build, and scale AI-powered systems that redefine how they operate and innovate. This role goes beyond building models — it's about designing agentic systems, AI-assisted workflows, and data-driven decision engines that help the company scale faster than headcount. You will be at the forefront of developing the next generation of autonomous systems that power both customer-facing products and internal operations — from optimizing payment experiences to accelerating development, testing, troubleshooting, and product creation.

This position will focus on two main aspects: maintenance and optimization of current AI solutions and services, and creation of new AI products. Our hiring partner already has a team of backend developers working on new products.

What You'll Do

AI Product Architecture & Development

• Architect, build, and deploy LLM-powered applications that augment and automate key workflows — from customer service and new product development to internal agentic workflows that optimize critical company processes.

• Design autonomous AI systems that can execute technical analysis, testing, troubleshooting, and decision-making at scale.

• Develop AI-driven tools that create measurable business impact — improving efficiency, accelerating innovation, and driving revenue growth.

Operational Intelligence & Scalability

• Identify areas where AI can generate efficiency gains — reducing manual work, optimizing processes, and enabling smarter operations.

• Build AI systems that enable scaling without exponential growth in headcount, thereby creating sustainable productivity and organizational intelligence.

Data & Model Optimization

• Lead fine-tuning and contextual optimization of AI models using proprietary data.

• Continuously refine performance through structured feedback loops, observability metrics, and user interaction data.

• Ensure adherence to privacy, compliance, and ethical AI principles in all model development.

Cross-Functional Collaboration & Innovation

• Work closely with data, product, and infrastructure teams to define the long-term AI roadmap.

• Experiment with emerging AI technologies to identify new capabilities that can drive differentiation and strategic advantage.

• Contribute to a culture of experimentation, rapid iteration, and continuous learning across the AI function.

What We're Looking For

• 5+ years of professional experience in AI/ML development, with at least 2 years focused on LLMs, RAG, or agentic systems.

• Strong engineering and product mindset — capable of balancing technical depth with strategic impact.

• Exceptional communication and collaboration skills to work across product, engineering, and data functions.

• Passion for pushing the boundaries of applied AI and creating systems that drive real business transformation.

Minimum Qualifications

• LLMs & RAG: Proven experience designing and deploying systems using models like GPT, Claude, Gemini, or similar — including Retrieval-Augmented Generation (RAG) pipelines and contextual retrieval systems.

• AI Agents & Multi-Agent Systems: Hands-on experience with Crew.ai, LangChain, LangGraph, or similar frameworks to build orchestrated agentic workflows.

• Fine-Tuning & Context Engineering: Expertise in supervised fine-tuning (SFT), LoRA, or custom dataset adaptation for domain-specific tasks.

• Programming & Frameworks: Proficiency in Python, GO and AI/ML libraries such as PyTorch, TensorFlow, or JAX.

• AI Infrastructure: Experience designing scalable, production-ready AI systems in AWS, GCP, or Azure, with a deep understanding of vector databases, model serving, and inference optimization.

• Observability & Monitoring: Familiarity with LangSmith, LangFuse, or equivalent tools for tracking, debugging, and evaluating LLM performance.

• API Integration: Expertise in integrating AI systems with RESTful APIs and internal platforms to create seamless, usable products.

• Proficiency with ML flow and LangChain.

• Good understanding of traceability tools.

• Extended backend experience is required.

• Minimum 2 years tenure in current company.

• Very good English communication skills (non-negotiable).

Preferred Qualifications

• Experience using LlamaIndex, Hugging Face, or similar open-source frameworks.

• Strong understanding of context optimization, embedding strategies, and knowledge retrieval.

• Familiarity with MLOps, CI/CD pipelines, and production deployment best practices.

• Prior experience in fintech, payments, or other data-intensive and regulated industries.

• Analytical rigor and ability to translate business objectives into measurable AI outcomes.

• Portuguese language skills.

What Our Hiring Partner Offers

• Competitive Compensation: $120,000 - $150,000 USD yearly (flexibility for exceptional candidates)

• Remote work - You can work from everywhere!

• Home Office Bonus - One time allowance to help you create your ideal home office.

• Work equipment

• Stock options

• Health Plan - Private medical insurance for you, your spouse, and your kids

• Flexible Days off

• Language, Professional and Personal growth courses

• For Brazil CLT hires: Additional benefits including groceries and other items

Culture

The culture is dynamic and collaborative. People are fun and at the same time clear about what they want. Team members are not afraid to ask for cooperation, collaboration, and input from peers in their department or elsewhere within the company. It's common to start a channel with three people from different teams and work together toward a solution in real time. Our hiring partner is looking for someone with a builder mentality who gets excited about working on new products and having the chance to be in a team where creativity is fostered.