Senior Software Engineer, Web SDK / Frontend Development

About Appier Appier is a software-as-a-service (SaaS) company that uses artificial intelligence (AI) to power business decision-making. Founded in 2012 with a vision of democratizing AI, Appier’s mission is turning AI into ROI by making software intelligent. Appier now has 17 offices across APAC, Europe and U.S., and is listed on the Tokyo Stock Exchange (Ticker number: 4180). Visit www.appier.com for more information. About the Role We are seeking a Senior Software Engineer who will primarily lead the development and evolution of the Appier Web SDK, while also contributing to frontend web UI development for enterprise-facing web applications. This position combines deep JavaScript engineering with frontend application development. You will work on improving the reliability, performance, and extensibility of Appier Web SDK, while also contributing to frontend architecture for enterprise-facing SaaS applications. Your work will directly impact how Appier’s AI capabilities are delivered and experienced at scale. You will collaborate closely with backend engineers, product managers, data teams, and UI/UX designers to deliver robust technical solutions that power Appier’s AI-driven products. [The seniority/title is determined by job-related skills, experience, and evaluation after the interview.] Why This Role Is Exciting You will work on real-world browser challenges, performance optimization, and SDK architecture — not just UI feature implementation You will have meaningful ownership while collaborating with experienced cross-functional teams Your work will directly power AI-driven experiences embedded in enterprise websites at scale Responsibilities Lead the long-term evolution of Appier’s Web SDK architecture, strengthening its scalability, modularity, and maintainability to support future product growth Design and refine a robust, extensible SDK foundation that can support multiple products, integration scenarios, and enterprise-scale deployments Continuously improve runtime performance, bundle efficiency, browser compatibility, and overall stability in diverse client environments Contribute to frontend application architecture for enterprise-facing web products, ensuring performance, consistency, and maintainability across shared components Identify technical debt and architectural risks early, and proactively implement sustainable improvements rather than short-term fixes Safeguard quality through thoughtful testing strategies and thorough code reviews, helping maintain a strong engineering culture Support production stability by investigating and resolving client-side issues when needed Participate in product and technical roadmap discussions to ensure the SDK platform evolves in alignment with business and platform strategy About You [Minimum qualifications] 5+ years of experience in frontend or JavaScript engineering Strong proficiency in JavaScript (ES6+) and TypeScript Deep understanding of browser internals, DOM, HTTP, web standards, and client-side performance optimization Experience designing or maintaining JavaScript SDKs, libraries, or shared frontend modules In-depth knowledge of front-end frameworks and technologies (e.g., React.js, Vue.js) and their ecosystems . Solid knowledge of version control (Git) and CI/CD workflows Experience writing unit, integration, and end-to-end tests Strong problem-solving skills and ownership mindset Self-motivated, proactive, and able to collaborate effectively in cross-functional teams Experience leveraging AI-assisted development tools (e.g., GitHub Copilot, Cursor, Windsurf) to accelerate coding, debugging, and refactoring. Familiarity with these tools is expected as part of our team’s daily development workflow. Passion for clean code, scalability, and performance, curious about new technologies and enthusiastic about developer experience [Preferred qualifications] Familiarity with modern build tools and bundlers (e.g., Babel, Webpack, Vite, Rspack, esbuild, etc.) Experience