Senior software engineer - 6 month O/IR35

Role overview Join a remote UK engineering team building embedded investment infrastructure used by fintechs, banks, and wealth firms across the country. This is a six-month contract under O/IR35, focused on designing, building, and operating reliable, testable services in TypeScript and Node.js that support regulated investment operations. The role is hands-on across the full lifecycle in a build-and-run model.

Responsibilities - Work in a cross-functional squad with engineering, product, and operations colleagues - Design, implement, and operate services within a domain-owned squad - Be accountable for the SLAs of products you own and drive iterative improvements - Maintain and extend service documentation and foster a culture of technical excellence - Provide guidance and mentorship for other engineers and answer non-technical queries about the platform - Participate in a structured on-call rotation

Requirements - Significant commercial experience with Node.js, specifically TypeScript - Hands-on experience with AWS and Serverless products such as Lambda, SQS, or API Gateway - Experience with document databases, ideally MongoDB - Experience mentoring engineers and leading technical delivery in a build-and-run model - Experience in structured on-call processes and incident management - Background in regulated industries, ideally financial services or FinTech

Nice to have - Experience building financial systems with multi-region, multi-currency, or trading-related complexity - Experience with a strongly or statically typed language beyond TypeScript - Experience designing workflow APIs with a focus on testing, observability, and performance