Principal Software Engineer

Location: Comunidad de Madrid, Spain

Principal Engineer / Domain Architect — Agentic Orchestration

About Sinch

Sinch is pioneering the way the world communicates. More than 150,000 businesses — including Google, Uber, Paypal, Visa, Tinder, and many others — rely on Sinch's Customer Communications Cloud to power engaging customer experiences through mobile messaging, voice, and email.

Whether you need to verify users or craft omnichannel campaigns, Sinch makes it easy. Our AI-infused Super Network, APIs, and applications ensure you can connect with your customers reliably and securely, at every step of their journey.

At Sinch we "Dream Big", "Win Together", "Keep it simple", and "Make it Happen". These values are our foundation.

The Role

The Agentic Orchestration domain builds the conversational AI and agentic layer of the Sinch portfolio: AI agents, reusable intelligence and ML capabilities, the Agentic Orchestration Platform, the Chatlayer agent builder, and the Context Store. Its job is to turn services that customers integrate by hand today into one coherent product that orchestrates conversations across channels, applications, and agents.

We are looking for a Principal Engineer to be the Domain Architect for this work. You will work across five teams of roughly 35 engineers in Spain, Belgium, Sweden, Germany, and Brazil, alongside the domain's product, design, and engineering leadership. You report to the Engineering Lead for the domain.

This is a hands-on role. Expect to spend about half your time writing code, mostly paired with engineers on the teams, in their codebases. The rest goes to architecture, cross-domain work, and building shared understanding of where the system is going and why.

You will have a large say in the technical future of conversations at Sinch.

How We Work

• Principles first. Coherence and quality come from a small set of principles that we hold to. You will help write them, defend them, and change them when they stop serving us.

• Pairing is the default. We pair and mob/ensemble to design, build, and spread knowledge. Architecture happens at the keyboard with the people who will own it.

• Experimental with AI tooling. Agentic coding tools are changing how software is built faster than anyone has settled practices for. We try things, measure what happens, and keep what works.

• Visual and shared. Diagrams, models, and maps are how we build shared understanding between engineers, product, design, and stakeholders. If it can't be drawn, it probably isn't understood yet.

Responsibilities

• Make sure the teams building Agentic Orchestration are asking the right questions; share and debate the architecture with them, then pair with them to build it.

• Own the domain's architecture: its boundaries, contracts, data flows, and the decisions behind them. Record decisions and their trade-offs so they can be revisited.

• Lead cross-domain initiatives. Work with principal engineers and architects across Sinch to solve, or propose solutions to, the hardest technical problems facing a large and complex company.

• Set the direction for agentic engineering principles and practices in the domain and lead their adoption, from how we use AI coding tools to how we design, test, and operate agent-based systems.

• Make and explain trade-offs under uncertainty: build vs buy, consolidation onto shared Sinch platform capability, deterministic vs agentic designs, speed vs operability.

• Create the diagrams, models, and narratives that let engineers, product managers, designers, and leadership reason about the system together.

• Grow technical leadership in the teams: coach tech leads and senior engineers, and raise the quality of design discussion across the domain.

Requirements

• 10+ years building software, including significant time as a principal, staff, or architect-level engineer on distributed production systems.

• Demonstrated commitment to engineering principles that keep a system coherent and of high quality, and a record of getting teams to adopt them.

• Extensive pair or mob programming, and the belief that it is a primary way to design and build software, not an occasional practice.

• Active, hands-on use of AI-based development tools (coding agents, LLM-assisted workflows) and an experimental mindset about where they help and where they don't.

• Deep understanding of complexity and complex systems: emergent behaviour, feedback loops, coupling, and how sociotechnical structure shapes architecture.

• Sound judgment on tradeoffs in uncertain environments, and the ability to explain the reasoning to both engineers and non-engineers.

• Strong visual thinker: you use diagrams and models to build shared understanding across engineers, stakeholders, and everyone involved in making the software.

• Polyglot: deep expertise in at least two languages, ideally including Java or another JVM language. Our systems are built mainly in Java and Go, with some TypeScript, and you can become productive in an unfamiliar language quickly.

• Strong understanding of how LLMs and agents work, and how to design reliable systems around them.

• Able to influence without authority across teams, domains, and seniority levels.

• Clear communicator in English.

Nice to Have

• Experience with Temporal or similar workflow orchestration platforms .

• Experience building conversational AI, LLM-based agents, or agent orchestration systems.

• Experience with messaging, voice, or other communications platforms at scale.

• Familiarity with event-driven architectures and cloud-native infrastructure on AWS or GCP.

• Experience with platform consolidation or migration across several products.

• Experience with domain-driven design, architecture decision records, or C4-style modelling.
  
  OUR HIRING PROCESS
  
  We are committed to ensuring a recruitment process that is fair, objective, consistent, and inclusive. Our approach includes structured, competency-based interviews designed to evaluate your skills, experience, and qualifications relevant to the role. At times, we may include a data-driven assessment to enhance our hiring success and identify candidates likely to excel.
  
  We believe in a two-way process and encourage you to ask questions throughout the journey. If this role isn’t what you’re looking for, please explore the other opportunities listed on our career page: https://www.sinch.com/careers/. No matter who you are, we hope you find an exciting path forward - hopefully with us!

The salary range for this role is €90,000–€130,000 per year, depending on your skills, experience and the impact you bring.