Job Staff AI Backend Engineer [Java/Kotlin] [EU-ONLY]. Remote, Penzance

About Kerno

Kerno is building the validation engine for AI-native backend development. As AI agents like Cursor and Claude Code become central to how developers write code, the need for fast, reliable validation grows with it. Kerno automatically generates, runs, and maintains validation tests (covering integration, performance, security, and resiliency) directly in the IDE or CLI, catching breaking changes and unintended side effects before code is merged.

We're a small, remote and fast-moving team solving a hard problem at the intersection of developer tooling, code analysis, and AI.

The Role

We're looking for a Staff AI Backend Engineer to help shape the core of our product. You'll work across the stack, from the validation and test generation agents to the backend platform and infrastructure. This is a high-impact role where your decisions directly affect the product our users rely on every day.

What You'll Do

• Design and build core components of Kerno's validation engine, code indexation, test generation and execution
• Work building AI agents that are in charge of test generation and code analysis
• Build and improve the platform layer local and/or remote environment orchestration
• Own features end-to-end: scoping, design, implementation, testing, and rollout
• Collaborate closely with the founding team on technical direction and architecture
• Help extend language and framework support as we grow beyond our current stack
• Contribute to the reliability and performance of a system that developers depend on for fast feedback

What We're Looking For

• 8+ years of professional backend development experience, with strong proficiency in Kotlin (or another JVM based language)
• Experience designing and building distributed systems or complex backend services
• Comfortable working with multiple languages, we use whatever is the best tool for the right solution
• Strong understanding of testing methodologies, CI/CD pipelines, and developer tooling
• Experience with or strong interest in AI agents development
• Familiarity with containerization and local environment orchestration (Docker, etc.)
• Experience working with databases
• Ability to work autonomously in a remote environment and communicate clearly in writing
• A product minded person, you care about why you're building something, not just how

Nice to Have

• Experience building developer tools, IDE extensions, or CLI tooling
• Experience with message brokers (Kafka, RabbitMQ)
• Familiarity with LLM APIs and prompt engineering in production contexts
• Experience at an early-stage startup

Why Kerno

• Hard problems: You'll work on code analysis, AI-powered test generation, and real-time validation. This isn't a simple CRUD API.
• High impact: Small team, direct influence on product direction and architecture
• Remote-first: Work from wherever you do your best work
• Quarterly off-sites: Meet your colleagues in person once a quarter
• AI-native: We're not adding AI as an afterthought. It's core to everything we build.
• Growing market: AI assisted development is exploding. The need for validation tooling is growing with it.