Senior .NET Engineer (Data Platform & AI Agents)

B3 Consulting Poland is part of an international organization listed on Nasdaq Stockholm, operating in 11 countries. The company operates with full autonomy in Poland, selecting its own technologies, processes, and ways of working while maintaining high professional standards. It delivers IT projects across a wide range of industries and technologies, both domestically and internationally.

• 5+ years experience building production, performant and scalable backend services in .NET/C# (preferably in multi-tenant SaaS environments)
• Strong SQL and PostgreSQL skills including schema design and query optimization
• Performance and memory awareness (streaming vs. buffering, profiling, load testing) and understanding of .NET architecture
• Daily experience working with AI/agents (e.g. Claude Code), turning requirements into agent-executable specifications and critically reviewing outcomes such as hallucinations, architectural drift, and security issues
• Testing and quality discipline, including unit and integration tests
• Excellent written communication skills for architecture documentation, specifications, and PR descriptions
• Fluent English (C1)
• Eligibility to work in Poland (citizenship, residence card, visa, etc.)

Nice to have:

• Experience with Microsoft Fabric or Spark
• Experience with MCP servers or exposing internal APIs as agent-callable tools
• Experience with LLM evaluation (evaluation suites, behavioral test design, benchmarking agent workflows)

• Designing and developing data platform services in a multi-tenant SaaS architecture (data ingestion, schema management, snapshots, calculated fields, exports) using .NET, Entity Framework, Dapper, and PostgreSQL
• Building tools that dynamically generate performant queries tailored to each customer's unique data model, with focus on performance and cost optimization (bulk ingestion, streaming, complex SQL queries)
• Developing agentic tooling supporting the team's work (custom skills and sub-agents, MCP tools exposing internal APIs)
• Collaborating with Data Platform, Analytics, Support, and Product teams to ensure the quality of AI-generated code

Eligibility to work in Poland (citizenship, residence card, visa, etc.)