Principal Software Engineer (AI)

Location: Hybrid in Comunidad de Madrid, Spain, with Sweden also listed as a location.

Salary: €90,000–€130,000 per year, depending on skills, experience, and impact.

Company

Sinch builds a Customer Communications Cloud for mobile messaging, voice, email, conversational AI, and customer engagement.

What you will do

• Own the Agentic Orchestration domain architecture, including boundaries, contracts, data flows, and architecture decisions.
• Pair with engineers across five teams to design and build production systems.
• Lead cross-domain initiatives and solve complex technical problems with principal engineers and architects.
• Set engineering principles and practices for AI coding tools, agent-based system design, testing, and operations.
• Evaluate trade-offs including build versus buy, platform consolidation, deterministic versus agentic designs, and speed versus operability.
• Create diagrams, models, and narratives while coaching tech leads and senior engineers.

Requirements

• 10+ years of software development experience, including significant experience as a principal, staff, or architect-level engineer on distributed production systems.
• Demonstrated commitment to engineering principles that maintain system coherence and quality, with a record of team adoption.
• Extensive pair or mob programming experience and a belief that it is a primary design and development practice.
• Active hands-on use of AI-based development tools, including coding agents and LLM-assisted workflows, with an experimental mindset.
• Deep understanding of complexity and complex systems, including emergent behaviour, feedback loops, coupling, and sociotechnical architecture.
• Sound judgment in uncertain environments and the ability to explain technical reasoning to engineers and non-engineers.
• Strong visual thinking and use of diagrams and models to create shared understanding.
• Deep expertise in at least two programming languages; Java or another JVM language is preferred. The main systems use Java and Go, with some TypeScript.
• Strong understanding of LLMs and agents and how to design reliable systems around them.
• Ability to influence across teams, domains, and seniority levels without formal authority.
• Clear communication 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 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.

Culture & Benefits

• Principles-first approach focused on coherence and quality.
• Pairing and mob/ensemble programming are the default ways to design, build, and share knowledge.
• Experimental use of AI tooling, with practices measured and retained based on what works.
• Visual collaboration through diagrams, models, and system maps.
• Structured, competency-based interviews designed to support a fair, objective, consistent, and inclusive process.

Hiring process

• Expect structured, competency-based interviews assessing skills, experience, and qualifications relevant to the role.
• A data-driven assessment may be included as part of the recruitment process.