Principal Software Engineer – .NET, AWS & AI

Are you excited by the opportunity to shape the future of high-performance, scalable, reliable, and resilient enterprise software? Thomson Reuters is seeking a hands‑on Principal Software Engineer with deep, recent C#/.NET Core and AWS experience building large-scale distributed systems and cloud‑native platforms, along with experience applying AI/ML, Generative AI, large language models (LLMs), retrieval‑augmented generation (RAG), or agentic AI capabilities in production environments.

This is a Principal‑level individual contributor role requiring demonstrated ownership of architecture and technical direction for complex, enterprise‑scale production systems. The successful candidate will have operated at Principal Engineer or equivalent scope, influencing multiple engineering teams while remaining actively hands‑on with architecture, design, development, and implementation.

You will play a key role in the modernization and evolution of our U.S. tax compliance solutions, helping establish technical direction, improve platform scalability and reliability, and responsibly incorporate AI‑enabled capabilities into our products. Candidates outside the Washington, DC area must be willing and able to travel to the Washington, DC office as needed.

Own architecture and system design for complex, large‑scale production platforms, making technical decisions around scalability, reliability, performance, security, and maintainability.

Design and build production software using C#/.NET Core and AWS, remaining actively involved in implementation, technical problem‑solving, design reviews, and engineering delivery.

Lead the modernization of complex legacy applications into cloud‑native architectures, including distributed systems, microservices, APIs, data services, and containerized workloads.

Establish technical direction and influence architecture and engineering decisions across multiple teams.

Provide hands‑on technical leadership through architecture and design reviews, code guidance, troubleshooting, mentoring, and engineering best practices.

Identify and help implement opportunities to incorporate AI/ML and Generative AI capabilities into production products.

Contribute to the long‑term technical roadmap and communicate architecture decisions, trade‑offs, risks, and recommendations.

You're a fit for this Principal Software Engineer role if you bring:

• 10+ years of professional software engineering experience with demonstrated Principal Engineer or equivalent senior individual contributor scope.
• Strong, recent, hands‑on C#/.NET Core engineering experience, including personally designing and implementing production software.
• Deep, hands‑on production experience with Amazon Web Services (AWS), designing and implementing cloud‑native systems using multiple AWS services such as EC2, S3, Elastic Load Balancing, Auto Scaling, RDS, Lambda, SQS, and container services.
• Proven experience architecting and implementing large‑scale distributed systems, microservices, APIs, and highly available production applications.
• Demonstrated experience modernizing complex legacy applications into scalable, resilient cloud‑native solutions.
• Principal‑level architecture and system design ownership, including making significant technical trade‑offs, setting technical direction, and influencing engineering decisions across multiple teams.
• Proven ability to remain hands‑on with engineering delivery while providing Principal‑level technical leadership.
• Strong knowledge of software architecture, object‑oriented design, data structures, algorithms, design patterns, API design, relational databases, and modern engineering practices.
• Strong communication and collaboration skills with the ability to influence across…