Senior AI Fullstack Engineer (Next.js & LLM)

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

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