Senior Fullstack Engineer - AI-Driven Workflow Automation

About the Role

We're hiring a Senior Fullstack Engineer to join our remote team in Romania. At AiSentr, we're building a platform that simplifies the implementation of AI into business workflows for companies lacking in-house data science or engineering capabilities. As a Senior Fullstack Engineer, you'll work across our entire product surface, from frontend to backend, and the AI orchestration layer that connects them. This role offers you the opportunity to build great products for enthusiastic customers while working in a supportive and innovative environment.

What You'll Do

• Develop and ship features end-to-end: from responsive, performant UI in React and Next.js, through REST APIs in NestJS, to data persistence in Postgres and MSSQL.
• Implement real-time experiences using SSE for streaming LLM responses to users.
• Design and build workflow nodes - the core building blocks of our automation platform - with clean interfaces and predictable behavior.
• Work directly within our AI agent orchestration layer (Mastra), defining tools, composing agents, and shaping how our product reasons and acts on behalf of users.
• Evaluate architectural trade-offs pragmatically, aiming for the simplest solution that works well.

Requirements

• 5+ years of commercial experience building and shipping web applications across frontend and backend.
• Strong proficiency in TypeScript, with a genuine understanding of the language and its type system.
• Deep experience with React, including rendering behavior, hooks, performance optimization, and component composition.
• Solid backend experience with Node.js; familiarity with NestJS is a plus.
• Comfort working with relational databases (Postgres, SQL Server), including writing queries and designing schemas.

Nice to Have

• Experience with AI agent frameworks or orchestration tools (Mastra, LangChain, CrewAI, or similar).
• Familiarity with Azure services, particularly AKS, Blob Storage, or AI Search.
• Experience with SSE or WebSocket implementations for real-time streaming interfaces.

What We Offer

• A competitive long-term B2B contract (or FTE if preferred).
• Fully remote work based in Romania.
• A small, senior team where your work has direct, visible impact on the product and the business.
• A working environment that values clarity, tests, and documentation over cleverness.