Senior Software Engineer (C# / PostgreSQL / AI-Native)

zendbox; Whetsted; On-site; GBP 60,000 - 80,000; Full time

Job summary

A leading tech company in the United Kingdom seeks a Senior Software Engineer to architect and build a production-grade, AI-first .NET platform. This role involves transforming AI workflows into resilient production code, designing the infrastructure for high-concurrency workloads, and adopting AI-assisted tools to enhance development velocity. The ideal candidate will have mastery in C#, expertise in PostgreSQL, and an architectural mindset to ensure scalability. Join a high-velocity team that prioritizes fast iterations and innovative solutions.

Qualifications

• Expert in the modern .NET ecosystem.
• Design schemas and optimize queries for PostgreSQL.
• Ability to scale PoC to handle increased loads.

Responsibilities

• Transform raw AI prompts into production code using .NET 10/C# 14.
• Design and build AI interaction frameworks.
• Implement safeguards for AI outputs.
• Design and deploy cloud infrastructure for AI workloads.
• Lead the adoption of AI-assisted development workflows.
• Collaborate on the technical roadmap for AI systems.

Skills

C# Mastery

PostgreSQL Expert

Architectural Thinker

Tools

.NET

Azure

AWS

Blazor

Job description

We have a working AI Proof of Concept (PoC) that proves our vision; now we need the engine that powers the product at scale. As our Senior Software Engineer, you will be the lead architect and primary builder of our production-grade, AI-first .NET platform.

Working directly with the Head of Technology, you will be responsible for moving us from experimental scripts to a robust, observable, and scalable Agentic AI Architecture. We are a high-velocity team that values "Ship Fast, Fix Fast." We utilize agentic AI tools like Claude Code to bypass the boilerplate, freeing you to focus on the high-value architectural challenges of a production-ready system.

What You'll Do

• Productionize AI Workflows: Transform raw AI prompts and experimental logic into resilient production code using .NET 10/C# 14.
• Architect Agentic Systems: Design and build the "Agent Loops" (Planning → Execution → Observation) that allow our AI to interact reliably with our internal databases and external APIs.
• Build for Reliability: Implement "Evals" and Guardrails to manage the non-deterministic nature of LLMs, ensuring outputs are safe, accurate, and consistent for our users.
• Cloud Infrastructure: Partner with the Head of Tech to design and deploy the Azure/AWS infrastructure required to support high-concurrency AI workloads, focusing on latency and cost-per-token optimization.
• AI-First Tooling: Lead the team in adopting and optimizing AI-assisted development workflows (Claude Code, Cursor, etc.) to maintain our 10x velocity.
• Strategic Evolution: Collaborate on the long-term technical roadmap, identifying when to use fine-tuned Small Language Models (SLMs) vs. Frontier LLMs.

Requirements

The Must-Haves

• C# Mastery: You are an expert in the modern .NET ecosystem.
• PostgreSQL Expert: You know how to design schemas, optimize queries, and leverage Postgres for high-performance applications.
• Architectural Thinker: You can look at a PoC and know exactly what it needs to survive 100x the current load.

Bonus Points (Will make you stand out)

• Blazor: Experience with Blazor (Server or WebAssembly) for building real-time UIs.
• Azure ML: Any exposure to Azure Machine Learning services or deploying ML models into a production pipeline.
• AI Workflow: You already use Claude Code, Cursor, or GitHub Copilot in your daily flow.