Senior Product Engineer (Full Stack)

Senior Product Engineer (Full Stack) About the Role Company Overview STRACT provides the AI shopping app "PLUG". We partner with over 2,000 domestic e-commerce sites to aggregate them, enabling anyone to easily enjoy a safe and smart online shopping experience by automatically comparing the lowest prices, offering coupons, and cashback. We started with the unique technology of an iPhone Safari extension to reinvent the e-commerce platform for the AI era. Currently, we have reached 2 million downloads (as of July 2025) and surpassed 10 billion JPY in annual gross merchandise volume, establishing our market presence. Now, we are expanding our product to establish a position that covers the entire funnel from search and recommendation to the point of purchase. Materials: Pitch Video: https://youtu.be/OZ4qlcfH9tM Service Site: https://lp.plugapp.jp/ Our Vision for "Senior Product Engineer" At STRACT, we consider this position to be of utmost importance. The title "Senior Product Engineer" embodies our commitment to the product "PLUG," where each engineer brings their high technical skills and experience to sincerely improve user experience and value, driving product and business growth. STRACT, which has honed its product by obsessing over the "interface," aims to "create a visionary company that lasts for 100 or 200 years" and "invest in the social implementation of technologies that can become next-generation infrastructure." With this grand goal, we released the PLUG business using reverse thinking. We are convinced that product growth is the most crucial factor for structural company growth. Therefore, our team culture is to approach and commit to the business as a "product" unit, rather than simply segmenting software development, growth hacking, business model construction, and user experience design. At STRACT, we define "Senior Product Engineer" as an individual who can autonomously and at a high level drive progress in all areas. We consider "product sense," "domain knowledge," "technical skill," and "hypothesis testing ability" to be the four key elements. For more details, please refer to the following article. Article: https://note.com/hkrit0/n/n23acbc06ff68 Hiring Background From the user's perspective, PLUG is currently one of the apps that utilize browser extensions. However, the development domain is broad and highly complex, making it extremely challenging to develop. It is necessary to integrate with various e-commerce sites and user journeys to create economic conversions. The number of user touchpoints is very high, making interface development capabilities even more crucial. The position, which assists in the last mile of conversion through browser extensions, has already created a certain market impact. From here, to update the entire e-commerce experience funnel, we are developing features that provide a seamless experience from the point of purchase, such as automation of purchases and payments, and post-payment services and guarantees, acting as an AI agent for shopping. We are looking for individuals who want to challenge themselves to create the best interface while leveraging advanced technology. Technical Challenges (Excerpts) Pursuit of Refined UI Balancing Functionality and Beautiful Interaction In PLUG, we face the unique challenges and excitement of developing not just feature-rich and convenient mobile app-like rich interactions, but also a "UI that naturally blends into any website" unique to browser extensions, which differs from general web app development. In PLUG, where the product value is significantly enhanced by interfaces designed to the pixel and seamless animations, we need engineers who can design and implement not just the surface but the entire experience. Complex Design Supporting Simple User Actions Behind the product, data processing of thousands of requests per second and cross-searching of product data on the scale of 10 billion items are running. These are realized by core technologies that support the "comfort," "accuracy," and "real-time performance" of the user experience. This is a highly rewarding environment for engineers who want to optimize the experience at the design level, not just the UI, with a Product Manager's perspective. Building and Technically Validating AI-Driven Development Environments We are currently actively promoting the integration and utilization of AI at the core of our engineering and product development. We need individuals who can technically lead the design and creation of systems to address the limitations of models, interface design challenges, and task structuring difficulties that cannot be solved by human review alone. At the product level, AI plays the following important roles: Supplementing product information and automatically generating specifications Automatic design and generation of structured databases Evaluating the reliability of product reviews Guarantee and credit assessment combining behavioral data and AI In particular, designing competitive advantages by linking proprietary internal data with AI involves complex considerations such as security, scalability, and ethics. Specific Responsibilities Lead UI design and implementation for the entire PLUG product (mobile and browser extension). Reproduce and optimize multi-functional UIs within the browser. Design UI/UX for value extraction through AI, such as AI-powered product data completion and automated browser checkout. Formulate specifications driven by user stories in collaboration with Product Managers and Designers. Participate in the upstream of feature development, starting with the definition of experiential value. PLUG is a product where a single line of code can change the internet experience itself. We want to shape that experience together with individuals who want to take responsibility for the product, including "how it will be used" and "how it will be delivered," not just "development." Please refer to the following article summarizing what the development team has been working on recently. Article: https://note.com/stract/m/m816d9a9e1a52 Development Environment We fully adopt TypeScript as our primary language, using it across frontend, backend, and infrastructure definitions. We manage almost all packages in a monorepo, enabling code sharing. Frontend: Next.js, ReactNative (Expo), Tailwind CSS Backend: Nest.js, TypeORM, MySQL, BigQuery, ElasticSearch, DynamoDB, MongoDB Infrastructure: AWS, AWS CloudFormation, AWS CDK, AWS ElasticBeanstalk, AWS RDS, AWS Glue, Firehose, GCP (BigQuery), Firebase (Hosting, Auth, Analytics), Segment, Sentry, Auth0 Data Analysis & Machine Learning: Jupyter Notebook, scikit-learn Development Environment: Git, GitHub, GitHub Actions, monorepo Development Flow: Git Flow Required Skills 5+ years of experience in web application engineering. Experience developing web applications using TypeScript. Experience developing API server applications. Experience designing relational databases (RDB). Systematic knowledge of software. Experience in code reviews for team members and maintaining/improving code quality. Ability to appropriately judge ticket granularity and development priorities. Fluent business communication in Japanese (approximately 10+ years of residency in Japan as a guideline). Preferred Skills Knowledge of target domains such as e-commerce/advertising. Development experience in both mobile and web applications. Experience developing AI products. Experience developing consumer services. Experience handling large-scale user data. Ideal Candidate Profile Empathy with STRACT's mission, vision, and values. Strong motivation to improve business and life through technology. Commitment to product creation and willingness to take responsibility. Ability to articulate "why something is good/bad" based on experience with many products. Ability to work autonomously in a small, elite team environment. Readiness to take responsibility for results and deliver output commensurate with high compensation. Ability to balance ideals and reality to make sustainable decisions. Visionary attitude to test one's abilities and take on challenges. Application Details Salary 20,000,000 JPY - 30,000,000 JPY *Negotiable within the above range based on experience. Work Location CIRCLES Ichigaya 7F, 4-19 Yotsuya, Chiyoda-ku, Tokyo Access: * 4-minute walk from "Ichigaya" Station * 4-minute walk from Exit 3 of "Ichigaya" Station (Toei Shinjuku Line, Tokyo Metro Yurakucho Line, Namboku Line) * 3-minute walk from Exit 6 of "Kojimachi" Station (Tokyo Metro Yurakucho Line) * 8-minute walk from Kojimachi Exit of "Yotsuya" Station (JR Chuo Line, Sobu Line) Employment Type Full-time employee Work System Primarily requires presence at the office at least 1 day per week / Discretionary labor system. Holidays & Vacations: * Complete two-day weekend system (Saturdays, Sundays, and public holidays) * Summer vacation * Year-end and New Year holidays * Paid leave * Congratulatory and condolence leave Probationary Period 3 months Benefits Various social insurances (for full-time employees) Commuting allowance Stock option system (for full-time employees) Company-issued laptop Unlimited access to 3D printers