Full Stack Engineer (LatAM)

About AfterQuery

AfterQuery is helping push the frontier of LLMs and AI Agents through novel datasets and experimentation. We work on building the most complex infrastructure that powers frontier data creation for agentic and hard reasoning workflows. We work with all 5 of the leading AI labs and are becoming the go-to partner for data infrastructure for YC companies. We have a sharp hockey stick growth rate and are extremely talent-dense, with most of our founding team coming from top IB and quant firms.

About the role

As part of AfterQuery’s engineering team, you’ll have end-to-end ownership over projects that push the frontier of AI evaluation. You’ll work on a mix of research engineering (designing novel RL environments, agentic systems, evaluation harnesses) and platform engineering (building human-in-the-loop platforms, scaling data infrastructure, designing annotator workflows).

This is not a narrow role. One week you might prototype a new RL environment from a research paper, the next you’ll be deploying distributed experiments on Kubernetes, and the week after you’ll be improving the reliability of our Next.js dashboards or building a Kafka pipeline for annotator analytics.

What You’ll Do

• Design and build scalable systems: RL environments, APIs, and human-in-the-loop platforms.
• Collaborate across research, product, and design to ship features quickly.
• Write clean, maintainable code and contribute to documentation.
• Participate in code reviews and design discussions
• Solve real-world scalability and reliability challenges.
• Contribute to the core infrastructure powering data and evaluation for leading AI labs.

What We’re Looking For

• Strong coding fundamentals in Node.js / TypeScript, Python and/or Go
• Deep understanding of distributed systems, scalability challenges, and system design.
• Familiarity with cloud platforms (GCP/AWS), Kubernetes, APIs, NoSQL databases.
• Ability to reason about trade-offs and balance speed vs reliability.
• Strong communication skills and a bias toward ownership, curiosity, and delivering simple solutions to complex problems.
• Bonus: Experience with RL environments, agentic systems, or human-in-the-loop workflows.

Why AfterQuery

• Fast-paced: Join a high-growth, talent-dense team moving quickly to define the future of data and AI evaluation.
• Cutting-edge data: Work directly with frontier labs and see model capabilities months before the market.
• Ownership: As one of the first engineers, you’ll have an outsized impact, shaping core systems from day one.