Principal Site Reliability Engineer

Commercetools; Greater London; On-site; GBP 120,000 - 180,000; Full time

Benefits offered by this job

Comprehensive health benefits

Learning and development

Family Leave Plus

Equity participation

Job summary

commercetools is hiring for a role focused on end-to-end AI capabilities, integrating agents with secure backends and live, streaming UI using generative-UI protocols.

You will leverage retrieval/embeddings, tool orchestration, and evaluation systems to ship production features with an AI spine across frontend, backend, and data layers.

Qualifications

• Shipped full-stack apps to production and owned them end-to-end: frontend through backend to deploy and operate, not handed off at a layer boundary
• 5+ years shipping production software, 2+ building with LLMs in production
• Hands-on experience with UI protocols (A2UI, AG-UI, MCP-UI, or similar). You've built against a generative/agent-driven UI protocol, not just consumed a REST API
• The AI spine: prompt/context engineering, agents, tool use, structured outputs, evals, MCP Python and TypeScript/Node + React; comfortable with async, streaming, and observability
• Working fluency with retrieval/embeddings and SQL

Responsibilities

• Build agent loops and orchestration: tool use, structured outputs, business-rule enforcement, graceful failure
• Build the integration layer (via MCP) that lets agents securely call backend systems and business APIs
• Render model output into live, streamed, accessible UI via generative-UI protocols
• Ground models in real data: retrieval, embeddings, and feedback loops that actually close
• Treat evals as a first-class system - provable improvement, not vibes
• Take a capability from prompt-in-a-notebook to a measured, guard-railed production feature

Skills

Full-stack

LLMs in production

UI protocols

AI prompts

Retrieval/embeddings

Tools

MCP

Python

TypeScript/Node

React

Job description

About commercetools

Real innovation starts with a strong foundation, and at commercetools, that comes from the perfect balance of our product and our people.

Behind every leap forward is a collective of builders, explorers, doers, makers, and problem-solvers.The kind of people who not only pioneered a more flexible approach to commerce architecture but also shaped the culture of experimentation that approach unlocked. Together they are the engine of commerce innovation today.

At commercetools, we power the next era of autonomous commerce for our customers. Whether it’s AI-driven solutions that help enterprises make smarter business decisions, bridging digital and physical shopping experiences, or enabling entirely new ways for industries to connect with their customers, we help the world’s most ambitious companies experiment, scale, and grow without limits.

Here the best idea wins, not the loudest voice. You will have the tools, trust, and space to not only build the future of commerce, but to build your own.

Your Impact

You own AI capabilities end-to-end: from the data and context that feed a model, through agent orchestration, to the generative UI a user sees and trusts. You've personally shipped and operated full-stack apps in production, so backend, frontend, data, and ML aren't four teams you coordinate with, they're four things you do. You're not a research scientist; you wield models and engineer ruthlessly around their uncertainty.

You will:

• Build agent loops and orchestration: tool use, structured outputs, business-rule enforcement, graceful failure
• Build the integration layer (via MCP) that lets agents securely call backend systems and business APIs
• Render model output into live, streamed, accessible UI via generative-UI protocols
• Ground models in real data: retrieval, embeddings, and feedback loops that actually close
• Treat evals as a first-class system - provable improvement, not vibes
• Take a capability from prompt-in-a-notebook to a measured, guard-railed production feature

This role is to based in our hubs - Berlin, Boston, Durham, Munich, London or Valencia.

What Sets You Apart

You're a creative problem-solver who is wired to find solutions. You confidently dive into complex challenges and have a talent for making them simple for others. Your curiosity drives you to constantly grow and contribute to an environment of trust and teamwork. Great ideas come from many paths, and your unique perspective matters more than checking every box. What matters most is the mindset you bring to the work.

You bring:

• Shipped full-stack apps to production and owned them end-to-end: frontend through backend to deploy and operate, not handed off at a layer boundary
• 5+ years shipping production software, 2+ building with LLMs in production (real users, not demos)
• Hands-on experience with UI protocols (A2UI, AG-UI, MCP-UI, or similar). You've built against a generative/agent-driven UI protocol, not just consumed a REST API
• The AI spine: prompt/context engineering, agents, tool use, structured outputs, evals, MCP Python and TypeScript/Node + React; comfortable with async, streaming, and observability
• Working fluency with retrieval/embeddings and SQL

Nice to Have:

• Fine-tuning/distillation, e-commerce or marketplace systems, and a track record in 0→1

Our Benefits

Because work and life are connected, our benefits are too. We’ve designed them to give you the security, flexibility, and opportunities you need to focus on what matters most.

Comprehensive health benefits for you and your dependents, including access to OpenUp for personalized mental health support

Learning and development opportunities including an annual learning budget, access to self-paced learning platforms and language training, personalized coaching, mentorship, and leadership programs

Family Leave Plus gives you additional fully paid weeks of parental leave on top of government-provided leave, so you can spend more time with your new addition

Our equity participation program allows you to share in our success

For more information on our benefits, visit this page.

Come as you are. Build with us.

Your unique perspective is essential to our success. We are committed to building a team that reflects the world around us because we know it’s the only way to build the future. We celebrate our differences and have created a hiring process that’s fair, inclusive, and designed to let your talent shine.

We proudly welcome applicants of every race, color, religion, gender identity, sexual orientation, age, and any other part of your identity that makes you who you are. As an equal opportunity employer, we believe that our strength lies in our diversity, and we invite you to be a part of our global community.

For more information on our diversity, equity, inclusion, and belonging practices, visit this page.