Senior Full-Stack Engineer (AI-Focused)

The Opportunity

An established SaaS product is rebuilding itself around AI, and this hire sits at the center of that shift, working side by side with the CTO. You'll put at least one AI feature in customers' hands within your first 90 days, and within a year your work should show up in adoption and retention numbers. Small team, real autonomy, and a product that already reaches millions of people.

A core piece of this work is the product's in app SDK, which runs inside customer applications and reaches millions of end users. You'll need to know what it takes to ship code that lives in other people's products: performance budgets, backward compatibility, versioning, and debugging in environments you don't control.

What You'll Own

- AI features from interface to model call: UI, services, APIs, and the LLM layer underneath

- The in product AI agent, making it genuinely useful to customers, from prompt design through production evals

- LLM pipelines that hold up under real traffic: RAG, tool calling, agent orchestration, and evaluation

- MCP integrations that let customers work with the platform straight from their own AI tools

- The in app SDK that runs inside customer products, keeping it fast, backward compatible, and easy to debug, along with the APIs behind it

- Speed, reliability and cost of every AI feature, with metrics that tie latency and quality to customer value

- The AI first roadmap and architecture, shaped together with the CTO and product

- How the team builds with coding agents: workflows, guardrails, and review norms others adopt

What We're Looking For

- 6+ years as a full stack engineer on production SaaS

- Strong TypeScript or JavaScript on both frontend and backend, including a modern frontend framework

- Solid Elixir and Python

- Hands on experience building and supporting SDKs used by external developers or customer applications: embedded web or JavaScript SDKs, Chrome extensions that load or invoke an SDK, or mobile SDKs (iOS, Android, React Native, Flutter)

- LLM features shipped to production: model APIs, RAG, tool calling or agents

- A track record of measuring LLM output quality, through evals or similar systems

- Working knowledge of WebSocket traffic at high volume and how it shapes architecture

- Daily use of AI coding agents, with clear judgment on where human review and guardrails belong

- C1 or C2 English, comfortable going deep with engineers and presenting tradeoffs to leadership

Nice to Have

- Built an MCP server, connector, or other agent tooling

- Hands on with LLM tracing and observability tools

- Background in onboarding, product adoption, or PLG products

Tools and Stack

TypeScript / JavaScript · Elixir · Python · WebSockets · LLM APIs · RAG · MCP · Claude Code · Web and Mobile SDKs · Chrome Extensions

Details

- Location: Remote, Argentina

- Time Zone: Strong overlap with US working hours required

- Salary: $84,000 - $100,000 usd yearly

- Type: Full time

About the Company

An established B2B SaaS platform that helps software companies onboard users and drive adoption through in app experiences. AI now sits at the core of its product strategy, and it reaches millions of end users across the US and Europe through its customers' applications.