Principal Engineer (Full Stack, Go / GCP / AI) in London

Requirements

• Principal or Staff Engineer experience in fintech or high scale SaaS, including regulated environments, with a proven record of personally shipping core platform or product capabilities (marketplaces, integrations, partner ecosystems, developer platforms).
• Strong production expertise in Go and modern backend engineering, including APIs, microservices, event driven and distributed systems, data handling, SRE practices, IaC (e.g. Terraform), and Kubernetes.
• Extensive hands on experience running production workloads on Google Cloud Platform (GCP), covering security, networking, IAM, deployments, observability, and cloud native operations.
• Full stack capability, taking product requirements from architecture through implementation to production operations.
• Recent hands on coding experience (last 6–12 months), with deep debugging skills, systems thinking, and ownership in live environments; experience implementing AI features in production (e.g. RAG, tool integration, evaluation, monitoring, model/vendor selection).
• Clear evidence of engineering passion: curiosity, craftsmanship, continuous learning, a strong bias to build, and a focus on simplifying complexity and improving developer experience in fast paced, regulated fintech or large-scale SaaS contexts.

What the job involves

• Synthix is building a SaaS native marketplace of financial solutions—a tech first platform that plugs into client workflows and connects them to an ecosystem of partners (banks, PSPs, ERPs, and data providers) through a single integration.
• We combine institutional credibility and reach with startup level engineering agility. We are deliberately strengthening our engineering capability with inspirational, hands on technical leadership—people who ship, raise the bar on quality, and deliver enterprise grade reliability at fintech speed.
• This is a builder role. You’ll be a Principal level engineer who codes regularly, sets technical direction through doing, and helps scale a high performance product engineering culture.
• A healthy, engaged and well-supported workforce are better equipped to do their best work and, more importantly, enjoy their lives inside and outside the workplace. That’s why we are committed to providing an environment with your development and wellbeing at its centre.
• Develop production ready features in Go, delivering robust backend services and APIs alongside full stack solutions spanning UI, data, performance, and operability.
• Establish and continuously improve engineering practices including service templates, libraries, developer experience (DX), and CI/CD pipelines.
• Provide technical leadership by clarifying architecture decisions, navigating trade offs, and defining clear “golden paths.”
• Mentor engineers to improve code quality, system design, debugging skills, and readiness for production deployment.
• Drive reliability and operational excellence through improved observability, incident response, resilience (SLOs, error budgets, postmortems), and scalable delivery processes.
• Build AI driven features with measurable impact, focusing on evaluation, feedback loops, safety, cost controls, and practical AI patterns such as retrieval, workflow automation, copilots, and intelligent triage.