Principal Software Engineer u2013 Full Stack (R3)

About the Technology Organization

Technology at Lilly builds and maintains capabilities using pioneering technologies like most prominent tech companies. What differentiates Technology at Lilly is that we create new possibilities through tech to advance our purpose u2013 creating medicines that make life better for people around the world, like data driven drug discovery and connected clinical trials. We hire the best technology professionals from a variety of backgrounds, so they can bring an assortment of knowledge, skills, and diverse thinking to deliver solutions in every area of our business.

About the Business Function

The Software Product Engineering (SPE) team is a specialised engineering group that delivers strategic solutions and differentiated capabilities. We take a forward-thinking approach, focusing on an enterprise platform and product mindset, ensuring that the solutions we build can be leveraged across Technology teams for broader impact and efficiency.

Job Title: Principal Software Engineer

Role Summary

As a Principal Software Engineer, you will lead the design, development, and delivery of business-critical applications across frontend, backend, and mobile systems. You will set engineering standards, mentor junior engineers, and drive technical excellence in cloud-native, scalable, and maintainable solutions. Your work will directly impact the reliability, performance, and value of our software products.

What You'll Be Doing

• Develop and contribute to frontend and backend frameworks supporting business-critical applications using JavaScript frameworks like ReactJS and Node.js.
• Design, develop, and maintain cross-platform mobile applications for iOS and Android using React Native, ensuring feature parity, native-quality performance, and a seamless user experience.
• Design and build scalable, reusable, and maintainable backend services and APIs with Node.js, Express.js, PostgreSQL, and cloud-native patterns.
• Replace commercial off-the-shelf (COTS) systems with modern, in-house scalable solutions leveraging AWS (ECS Fargate, Lambda, S3, RDS, CloudFormation, CloudWatch) and containerisation (Docker).
• Develop user-facing interfaces using React (Material-UI, Bootstrap, React Router, Redux Toolkit, Emotion, Next.js) and React Native with a focus on performance, accessibility, and Core Web Vitals.
• Coach and mentor junior engineers and help raise the overall technical bar.
• Define and maintain engineering standards, including CI/CD (GitHub Actions, Jenkins, AWS CodeBuild) and code quality practices (ESLint, Prettier, Husky, lint-staged).
• Collaborate across teams to deliver impactful features with measurable value.
• Leverage AI coding and reviewing tools such as GitHub Copilot, Cursor, and similar assistants to accelerate development workflows, improve code quality, conduct AI-assisted code reviews, and reduce boilerplate.
• Lead the authoring of technical documents, including high-level design documents, architectural blueprints, technical standards, and best practice guidelines to drive technical excellence and cross-team alignment.
• Demonstrate proficiency in prompt engineering to effectively guide AI coding tools (e.g., GitHub Copilot, Cursor) in generating optimal, context-aware, and secure code solutions.
• Use AI-assisted pair programming with tools like GitHub Copilot and Cursor to support rapid prototyping, test case generation, code review, and debugging.
• Encourage and mentor team members on responsible and secure use of AI in the software development lifecycle.

How You Will Succeed

• Design and implement robust APIs (RESTful) and microservices using Node.js and frameworks like Express.js or Koa.js.
• Build and manage scalable backend services with fault-tolerance, performance, and security in mind.
• Integrate with AWS cloud services and manage infrastructure with CI/CD tools like GitHub Actions or Jenkins.
• Work with databases such as MongoDB and PostgreSQL to store and retrieve structured and unstructured data efficiently.
• Build responsive and accessible UIs using React and cross-platform mobile experiences using React Native, with supporting libraries such as Material-UI, Bootstrap, React Router, Redux Toolkit, Emotion, Next.js.
• Implement modern UI development practices, including component-based design and state management (Redux, Context API).
• Collaborate with designers and UX teams to implement pixel-perfect interfaces.
• Optimise frontend and mobile applications for performance, Core Web Vitals, and platform-specific guidelines (Apple HIG, Material Design).
• Apply accessibility best practices and WCAG 2.2 standards.
• Lead code reviews, guide junior engineers, and build production-grade software.
• Contribute to open-source projects or lead technical discussions and architecture reviews.

What You Should Bring

• Strong proficiency in React.js and supporting libraries (Material-UI, Bootstrap, Redux Toolkit, React Router, Emotion, Next.js).
• Hands-on experience with React Native for building and shipping cross-platform mobile applications on both iOS and Android, including native module integration, app store deployment, and over-the-air updates.
• Solid understanding of JavaScript (ES6+), TypeScript (4.xu20135.x), HTML5, and CSS3/SCSS/Sass.
• Proficient in backend development with Node.js (20.x+), Express.js (4.17.x+), Feathers.js.
• Experience with RESTful and GraphQL APIs, microservices architecture, and real-time communication (e.g., WebSockets).
• Practical experience with AWS (ECS Fargate, Lambda, S3, RDS, CloudFormation, CloudWatch) and containerisation (Docker).
• Having AWS and Kubernetes certifications is a significant advantage and will be highly valued for this role.
• Familiarity with state management tools (Redux, Context API).
• Strong testing experience using tools like Jest, React Testing Library, Cypress, Playwright.
• Experience with mobile testing frameworks such as Detox or Appium, and familiarity with mobile CI/CD pipelines (e.g., Fastlane, App Center).
• Comfortable with frontend build tools like Webpack (4.x/5.x), Vite, Babel (7.x), Gulp, NPM, and linters like ESLint, Prettier, Husky, lint-staged.
• Experience working with CI/CD pipelines, source control (Git), and modern DevOps workflows.
• Demonstrated experience working with AI coding and reviewing tools such as GitHub Copilot, Cursor, and similar AI-assisted development environments for code generation, code review, and refactoring.
• Exposure to domain-driven design (DDD), serverless architecture, or event-driven systems.
• Knowledge of accessibility best practices and WCAG 2.2 standards.
• Experience in regulated industries (e.g., Life Sciences) is a bonus but not required.

Basic Qualifications and Experience Requirement

• Bachelor's degree in computer science, Computer Engineering, or a related technical field.
• 8+ years of hands-on software development experience across frontend and backend systems.
• At least 2 years of experience building and delivering mobile applications using React Native or comparable cross-platform frameworks.
• Demonstrated ability to lead code reviews, guide junior engineers, and build production-grade software.
• Strong foundation in computer science fundamentals, software architecture, and cloud-native patterns.
• Effective verbal and written communication skills.
• Ability to work collaboratively across backend, frontend, DevOps, and product teams.
• A high degree of intellectual curiosity and commitment to continuous learning.

Additional Skills/Preferences

• Familiarity with Core Web Vitals and frontend performance optimisation techniques.
• Experience with component-driven development using a design system (e.g., Material UI, Ant Design).
• Experience with native iOS (Swift) or Android (Kotlin) development as a complement to React Native.
• Familiarity with App Store and Google Play submission, review processes, and compliance requirements.
• Contributions to open-source projects or experience leading technical discussions and architecture reviews.
• Experience in regulated industries (e.g., Life Sciences) is a bonus but not required.

Lilly is dedicated to helping individuals with disabilities to actively engage in the workforce, ensuring equal opportunities when vying for positions. If you require accommodation to submit a resume for a position at Lilly, please complete the accommodation request form () for further assistance. Please note this is for individuals to request an accommodation as part of the application process and any other correspondence will not receive a response.

Lillyu00A0does not discriminate on the basis of age, race, color, religion, gender, sexual orientation, gender identity, gender expression, national origin, protected veteran status, disability or any other legally protected status.