Senior Software Engineer

The Senior Software Engineer will be a core member of the engineering team within the Knowledge & Innovation (K&I) department, responsible for designing, building, and operating the software systems that power the Firm's legal technology and AI initiatives. This role combines strong full-stack development skills with a focus on infrastructure, reliability, and the foundational systems that enable the team to ship and maintain production-grade tools at scale. This role will work across the full stack — building custom applications for attorneys and Professional Staff, establishing the engineering infrastructure that the team relies on (CI/CD, deployment pipelines, observability), and contributing to the design and implementation of AI-powered solutions. The Senior Software Engineer will collaborate closely with the Director of Engineering, data scientists, knowledge management professionals, and practice solutions teams to deliver tools that make a measurable difference in how the Firm operates. This is a hands-on, high-autonomy role on a small team where every engineer has significant ownership over the systems they build. JOB DUTIES & RESPONSIBILITIES: Software Development & Architecture Design, develop, and maintain custom software solutions supporting Knowledge & Innovation initiatives, including AI-powered tools, internal platforms, and integrations with existing Firm systems. Contribute to architectural decisions in partnership with the Director of Engineering, bringing practical perspective on tradeoffs between speed, reliability, and maintainability. Build and extend integrations across SaaS platforms, internal systems, data sources, and AI/LLM services used in legal workflows. Develop frontend experiences that are polished, consistent, and designed with care — including establishing and maintaining component libraries and design system foundations as the team's product surface grows. Infrastructure, Reliability & Observability Own and evolve the team's engineering infrastructure: CI/CD pipelines, deployment automation, infrastructure-as-code, and development environment tooling. Establish observability practices — monitoring, logging, alerting — so the team has confidence in the health and behavior of production systems. Partner with IT to navigate the Firm's infrastructure environment, coordinating on security protocols, cloud resources, and deployment targets. Ensure systems are reliable, secure, and aligned with Firmwide technology standards. AI & Legal Technology Solutions Contribute to the development of AI-powered tools — including retrieval-augmented systems, document analysis platforms, search tools, and workflow automation — working alongside product, data scientists, and the broader K&I team. Help translate complex legal and business requirements into practical, well-engineered software, collaborating with attorneys, knowledge management professionals, and practice solutions managers. Support adoption and iteration by interfacing directly with legal staff as needed — demoing tools, gathering feedback, and helping users get value from what the team builds. Collaboration & Craft Evaluate and prototype new tools, frameworks, and approaches that could improve how the team builds — bring experiments that work to the rest of the team. Help establish the engineering culture of a new function — contribute to decisions about how the team works, not just what it builds. EDUCATION: Bachelor's degree in Computer Science or related working experience. SKILLS & EXPERIENCE: Required 7+ years of experience in software engineering, with demonstrated progression in scope and responsibility. Strong full-stack skills across JavaScript/TypeScript, React, Node.js, and Python. Experience with cloud infrastructure (AWS and/or Azure), infrastructure-as-code (Terraform/Bicep), and CI/CD pipelines (GitHub Actions or equivalent). Practical experience with AI/LLM integration in production systems, or strong aptitude and interest in developing it. Experience with agentic coding tools (e.g., Claude Code, Cursor, Codex). Comfort working directly with non-technical stakeholders — able to demo work, gather feedback, and explain technical decisions clearly. Preferred Experience in legal technology, professional services, or other highly regulated environments. Experience establishing observability and monitoring practices (logging, alerting, dashboards) for production systems. Familiarity with design systems, component libraries, or frontend architecture patterns at the systems level. Experience integrating and extending enterprise SaaS platforms. Key Competencies Strong engineering judgment — knows when to build and what not to build. Comfort with ambiguity — can make progress with incomplete information and adjust as context develops. Pragmatic craftsmanship — cares about the quality and polish of what ships, without over-engineering. Curiosity and initiative — brings ideas, experiments, and improvements without being asked. Clear communication with both technical and non-technical audiences. Salary Information NY Only: The estimated base salary range for this position is $180,000 to $210,000 at the time of posting. The actual salary offered will depend on a variety of factors, including without limitation, the qualifications of the individual applicant for the position, years of relevant experience, level of education attained, certifications or other professional licenses held, and if applicable, the location in which the applicant lives and/or from which they will be performing the job. This role is exempt meaning it is not overtime pay eligible. Simpson Thacher will not sponsor applicants for work visas for this position. Privacy Notice For information about how Simpson Thacher & Bartlett LLP collects and processes your personal information, please refer to our Privacy Notice available at . Simpson Thacher & Bartlett is committed to a collegial work environment in which all individuals are treated with respect and dignity. The Firm prohibits discrimination or harassment based upon race, color, religion, gender, gender identity or expression, age, national origin, citizenship status, disability, marital or partnership status, sexual orientation, veteran’s status or any other legally protected status. This Policy pertains to every aspect of an individual’s relationship with the Firm, including but not limited to recruitment, hiring, compensation, benefits, training and development, promotion, transfer, discipline, termination, and all other privileges, terms and conditions of employment. #LI-Hybrid