Senior AI Fullstack Engineer (Next.js & LLM)

Senior • Remote

120 - 180 PLN/hr

Warsaw, Poland

About the Role

At Blazity, we are a team of React.js and Next.js experts building modern, API-first digital products for enterprise clients.

We are expanding our AI capabilities—autonomous agents, AI-driven automation, and LLM-powered workflows—and are looking for a Senior AI Fullstack Engineer who can design and ship production-ready AI systems.

You will work at the intersection of modern web architecture and generative AI, taking ownership of solutions delivered to real users.

Our requirements

Must-have Technical Excellence:

8+ years of experience as a consultant / forward deployed engineer
Strong experience with Next.js (App Router), React, TypeScript
Deep understanding of:
- Server vs Client Components (RSC)
- streaming, caching, revalidation, Server Actions
Vercel AI SDK / LangGraph / MCP
Experience building RAG systems
Claude extended thinking / prompt caching / Batch APIs

AI Engineering:

Proven experience shipping LLM-powered features to production
Hands-on with Anthropic / OpenAI APIs (messages, tool use, streaming)
Practical experience with:
- prompt engineering (structured output, few-shot, XML)
- tool calling / agent workflows
- multi-turn orchestration
Understanding of:
- token economics (input/output costs, context window)
- latency vs quality trade-offs

Reliability & Quality:

Experience with:
- prompt evaluations (LLM-as-judge, rule-based)
- handling hallucinations and failure modes
Ability to design robust AI systems, not just prototypes

Soft Skills:

Strong ownership mindset
Experience working directly with clients
Clear communication and structured thinking (English C1)
Ability to make decisions in ambiguous environments

Nice-to-have:

What You Will Do

Ship Production Apps: Build scalable web applications using Next.js (App Router) and TypeScript, ensuring high performance and clean architecture.
Engineer AI Workflows: Develop and orchestrate LLM-powered features using Anthropic and OpenAI APIs, focusing on tool use and streaming.
Agentic Orchestration: Design autonomous agent loops and multi-turn workflows, knowing when to use a structured pipeline versus a dynamic agent.
Optimize & Evaluate: Manage token economics (pricing, context windows) and implement prompt evaluations (LLM-as-judge, rule-based) to ensure system reliability.
Collaborate: Work directly with senior engineers, founders, and client teams to shape AI capabilities from concept to production.

What we offer

B2B: 120 – 180 PLN/h + VAT 🔥
100% remote (Poland)
29 paid vacation days
Private healthcare + sports card
High-impact work on real AI systems

Blazity Sp. z o.o.

Blazity Sp. z o.o. is a specialized company in the technology industry, focusing on React.js and Next.js development. The company is dedicated to building API-first products and actively contributes to the open-source ecosystem. Blazity positions itself as a long-term technology partner for its clients while also investing significantly in its internal open-source software (OSS) initiatives. The company values a proactive and ownership-driven mindset, strong communication skills, and a passion for open-source development. Blazity operates with a flat organizational structure, minimizing bureaucracy to maintain simplicity and efficiency. The company supports remote work, particularly from Poland, and offers flexible working hours to accommodate personal schedules. Blazity fosters an open and supportive environment, encouraging feedback and team collaboration. The company is distinguished by its commitment to having a genuine impact on its decisions and direction, as well as its emphasis on team involvement in shaping its future.

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