Principal Software Engineer - CoreAI

Job ID: 200046142Posted: 2026-09-08Location: United States, Washington, RedmondSalary: USD $142,800 - $274,800 per yearEmployment type: Full-TimeWork site: 3 days / week in-officeRole type: Individual ContributorTravel: Less than 25%Profession: Software EngineeringDiscipline: Software EngineeringCompany: MicrosoftOverviewDo you want to build the AI platform that trains the world’s most advanced models? Join CoreAI, where we’re building next-generation systems for large‑scale reinforcement learning. Our platforms power the full lifecycle of cutting‑edge LLMs – from rapid experimentation to global production deployment. On our team, you’ll play a pivotal role in making large‑scale post-training and reinforcement learning workflows faster, safer, and more reliable. You’ll: Build and evolve distributed services that underpin massive training runs Improve iteration loops for researchers and engineers Debug complex interactions between models and hardware Apply advanced performance optimization techniques that directly impact product quality and operational excellence Develop deep expertise in ML systems, AI infrastructure, and compute orchestration Ship platform capabilities that enable mission‑critical AI workloads for customers around the world Microsoft’s mission is to empower every person and every organization on the planet to achieve more, and we’re dedicated to this mission across every aspect of our company. Our culture is centered on embracing a growth mindset and encouraging teams and leaders to bring their best each day. Join us and help shape the future of the world.ResponsibilitiesAI-Native Development Improves artificial intelligence (AI) tools and practices across the software development lifecycle (SDLC). Proactively takes responsibility for the content of their AI-generated requirements, design documents, code, and other assets, assisting other members of the team to do the same. Incorporates Responsible AI practices into the SDLC to ensure appropriate controls over AI-generated assets. Applies SDLC and engineering health measures (e.g., Accelerate, SPACE framework, Engineering System Success Playbook [ESSP]) to guide improvements to processes and practices, especially those involving AI. Experiments with AI tools and practices to improve their own capabilities, and provides recommendations on how to adopt them to other members of the team. Coding Leads by example across teams and mentors others to produce extensible, maintainable, well-tested, secure, and performant code used across products that adheres to design specifications. Leads efforts to continuously improve code performance, testability, maintainability, effectiveness, and cost, while learning about and accounting for relevant trade-offs. Identifies best practices and coding patterns (e.g., leveraging state-of-the-art generative artificial intelligence [GenAI], approaches to source code organization, naming conventions) and provides deep expertise in the coding and validation strategy. Creates and applies metrics to drive code quality and stability, appropriate coding patterns, and best practices. Identifies and anticipates blockers or unknowns during the development process, escalates them, communicates how they will impact timelines, and then leads efforts to identify and implement strategies and/or opportunities to address them. Design Owns and leads efforts and discussions for the architecture of aspects of complex products/solutions (e.g., design, cost). Leads the testing and exploration of various design options across a set of complex product/solution scenarios, ensuring the strengths and weaknesses of each option are outlined and making recommendations for which design option is best. Creates proposals for architecture and design documents, and leads testing of hypotheses and proposed complex solutions. Shares and acts on findings from investigations, owns design decisions, and oversees the less experienced team members. Leads the development of design documents that support user stories and other product requirements. Evaluates new technologies to solve classes of problems, and determines how to integrate these technologies within existing systems. Leads design discussions with the team and shares findings/learnings from investigations, holding ownership for design decisions. Leads efforts to ensure system architecture and individual designs meet performance, scalability, resiliency, disaster recovery, cost of goods sold (COGS), and other requirements and expectations. Upholds Microsoft standards of security, privacy, and other compliance requirements and expectations. Understands and coaches less experienced engineers on the importance of building solutions that expand upon the work of others. Leads the refinement of products through data analytics, and makes informed decisions in engineering products through data integration. Reviews complex designs/architectures within and across teams to provide recommendations for improvements. Engineering Excellence Leads efforts to use and enhance, or build, new software developer tools to support easier, faster, and more effective software engineering across products. Identifies whether open source or internal code is available to address coding needs for a set of products, and reuses it in a responsible manner where applicable. Develops substantial skills in tools inside and outside current areas of expertise. Leads identification and/or creation of tools that are useful for building the product. Shares best practices and teaches others about new tools and strategies. Implement Leverages their subject-matter expertise to partner with appropriate stakeholders (e.g., technical program managers) to drive multiple groups' project plans, release plans, and work items. Breaks down long-term project vision into milestones as part of an overall roadmap. Guides other members for project estimation and escalates issues that might cause a major delay. Drives efforts to ensure required security protections and detection processes are accounted for in planning. Drives efforts to ensure project plans adhere to security, privacy, and compliance requirements. Drives efforts to ensure all code for a set of products/solutions is properly flighted for quicker mitigation of production incidents. Calculates capacity for planning, accounting for appropriate failover and backup/restore mechanisms for disaster recovery for a set of products and/or solutions. Makes considerations for efficient operation of a set of products and/or solutions after it is live. Proactively establishes rollback plans for a set of products and/or solutions. Reliability and Supportability Maintains operations of live site service, following security best practices when responding quickly to mitigate issues while using the minimum required permissions to do so that arise on a rotational, on-call basis. Implements and helps others implement solutions and mitigations to complex issues impacting the performance or functionality of live site services. Reviews and writes incident postmortem and presents insights that drive changes to reduce or eliminate incidents. Proactively improves troubleshooting guides (TSGs), wikis, tests, and telemetry to make on-call better, and recommends user-facing support documentation and additional test coverage to reduce likelihood of future user-initiated incidents. Enables secure operations, security monitoring, and integration with live site investigation activities. Proactively identifies opportunities (e.g., lunch talks, automation, practices, tools) that can be leveraged to improve the live site experience and executes on themQualificationsRequired/minimum qualificationsBachelor's Degree in Computer Science or related technical field AND 6+ years technical engineering experience with coding in languages including, but not limited to, C, C++, C#, Python, or Java, OR equivalent experience.Other Qualifications:Ability to meet Microsoft, customer and/or government security screening requirements are required for this role. These requirements include, but are not limited to the following specialized security screenings: Microsoft Cloud Background Check: This position will be required to pass the Microsoft Cloud background check upon hire/transfer and every two years thereafter.Preferred QualificationsMaster's Degree in Computer Science or related technical field AND 8+ years technical engineering experience with coding in languages including, but not limited to, C, C++, C#, Python, or JavaOR Bachelor's Degree in Computer Science or related technical field AND 12+ years technical engineering experience with coding in languages including, but not limited to, C, C++, C#, Java, JavaScript, or PythonOR equivalent experience.Prior experience in reinforcement learning, post-training, and container workloads preferred.Hands-on experience with inference technologies such as vLLM, SGLang, and disaggregated inference.Experience with training and orchestration technologies such as VERL, Slime, and Ray.Deep knowledge of containers, GPU computing, and distributed training infrastructure.Demonstrated ability to modify, optimize, or improve models and training/inference systems, rather than simply using the technologies.Prior experience in cloud software development.Software Engineering IC5 - The typical base pay range for this role across the U.S. is USD $142,800 - $274,800 per year. There is a different range applicable to specific work locations, within the San Francisco Bay area and New York City metropolitan area, and the base pay range for this role in those locations is USD $188,000 - $304,200 per year. Certain roles may be eligible for benefits and other compensation. Find additional benefits and pay information here:This position will be open for a minimum of 5 days, with applications accepted on an ongoing basis until the position is filled.Microsoft is an equal opportunity employer. All qualified applicants will receive consideration for employment without regard to age, ancestry, citizenship, color, family or medical care leave, gender identity or expression, genetic information, immigration status, marital status, medical condition, national origin, physical or mental disability, political affiliation, protected veteran or military status, race, ethnicity, religion, sex (including pregnancy), sexual orientation, or any other characteristic protected by applicable local laws, regulations and ordinances. If you need assistance with religious accommodations and/or a reasonable accommodation due to a disability during the application process, read more about requesting accommodations.