Senior AI Fullstack Engineer (Next.js & LLM)

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.

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
• Experience with Vercel AI SDK / LangGraph / MCP
• Experience building RAG systems
• Knowledge of 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) and latency vs quality trade-offs

Reliability & Quality:

• Experience with prompt evaluations (LLM-as-judge, rule-based) and 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

• 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.

Only candidates located in Poland are eligible for this 100% remote position.