AI Fullstack Engineer (Python, Java, Typescript)

Expected, Python, Java, TypeScript

Operating system, macOS

About the project, You will be cooperating with a leading provider of AI evaluation and optimization solutions, trusted by multinational companies to optimize AI agents and detect performance issues in large language models., In this role, you will contribute to a product that addresses one of the most important and challenging problems facing society’s adoption of AI today.

Your responsibilities, Build RL environments end-to-end: frontend interfaces, backend services, APIs, data models, and workflows - using technologies like TypeScript, Python/FastAPI, Java, and Postgres., Build tooling and shared services, like agentic systems and frontends for trajectory review, verifier debugging, and reward hacking checks., Work with AI coding tools (Claude Code, Codex, and similar) to generate ideas for extending them and building new tooling on top., Design efficient data models and REST APIs., Develop internal tools and libraries (e.g. a data visualization library) to improve productivity across the engineering team.

Ability to work 2:00 p.m. - 10:00 p.m. (CEST)., Proven experience in building and maintaining production-ready agentic systems (custom evaluation harnesses)., A solid understanding of how modern LLMs work at the API level - tool calling, agent loops, context management - and experience building custom tools, harnesses, or non-trivial agent integrations., 5+ years as a software engineer, full stack engineer, or similar., Experience with Java, Python and backend frameworks like FastAPI or Django., Strong experience building production software with TypeScript., Strong experience designing APIs, services, data models, and workflows — ideally with TypeScript, Python, FastAPI, Java, and Postgres.

Optional, BS/MS in Computer Science, Mathematics, Statistics, or a related quantitative field., Experience with Next.js and Material UI., Experience with cloud environments like AWS., Familiarity with vector and columnar databases., Due to the client’s time zone, we would appreciate a candidate who can work until 10:00 p.m.

What we offer, Sport subscription, Private healthcare, Flat structure, Small teams, International projects

Benefits, sharing the costs of sports activities, private medical care, remote work opportunities, flexible working time, extra social benefits, baby layette, school layette, employee referral program, charity initiatives, Gift vouchers for kids (birthdays, Christmas, Child's Day)

Recruitment stages, HR call (15 min.), Technical call with our team (+/-45 min.), Meeting with our Client (30 - 60 min.)

Join us and make a real impact! , If you’re ready to broaden your horizons and work with an innovative company at the forefront of AI, we’d love to hear from you. You’ll help build the environments that shape how future AI systems are trained, evaluated, and aligned - and collaborate with world-class engineers and researchers on one of the most important technical challenges of our time.

ACAISOFT POLAND Sp. z o.o., Acaisoft is a Polish company partnering with industry leaders across healthcare, telecom, fintech, and insurance. We specialize in delivering cloud-native, data-driven, and scalable solutions for enterprises operating in fast-moving environments. We currently serve around 30 active customers worldwide, mostly based in the U.S. We specialize mainly in:, * Data Engineering & AI, * Cloud-Native Solutions, including Cost Optimization, * Platform Engineering, Since technology is constantly being developed at such a fast pace, we always strive to be one step ahead of the market and keep up with the latest solutions.