Full Stack Engineer

About the COOL company

The COOL company is a global leader in AI-powered advertising technology, helping brands, agencies, and publishers simplify advertising and amplify performance.

Powered by COOL AI, our intelligent platform unifies creative generation, media activation, optimization, and attribution into one continuously learning system. Instead of relying on fragmented tools and manual campaign management, COOL AI executes thousands of real-time micro-optimizations across search, social, display, video, and connected TV-helping customers launch faster, optimize continuously, and achieve stronger business outcomes.

Our innovation and growth have earned industry-wide recognition, including being named a 7-time recipient of the Inc. 5000 list of America's Fastest-Growing Private Companies, a 2-time Deloitte Technology Fast 500 honoree, recognized on Crain's New York Fast 50, honored by the Digiday Media Awards for helping modernize digital media, and named one of Adweek's Top 10 Fastest Growing Solution Providers globally.

We're building the future of advertising, where every signal becomes intelligence and every optimization drives performance. As we continue to grow globally, we're looking for curious, ambitious people who want to work with cutting-edge AI technology, solve complex challenges, and help redefine what's possible in modern advertising.


About the Role

We are looking for a Mid-Senior Full-Stack Engineer to join our Product Engineering team, reporting to the Engineering Manager (Bi Yoo). This role is responsible for building and maintaining the web applications that power our advertising platform, including the Cool AI campaign management system, billing and invoicing module, and advertiser-facing dashboards. The Full-Stack Engineer will work across our frontend (React/TypeScript) and backend (Java/Spring Boot) stack, delivering features end-to-end from database schema design through API development to polished UI implementation.


Challenges and Opportunities

This role spans the full product surface of a growing ad tech platform. You'll build features that advertisers interact with daily - campaign creation and launch workflows, real-time performance dashboards, multi-platform account

integrations (Google Ads, Meta, Adform), and automated billing systems. There is significant opportunity to shape product architecture as we scale to support new advertising channels, expand our AI-driven campaign optimization, and

onboard enterprise clients with complex billing and permissions requirements.


Responsibilities and Duties

• Design and implement full-stack features across React (TypeScript, Tailwind CSS, Vite) and Spring Boot (Java 17, PostgreSQL) codebases
• Build and maintain RESTful APIs with proper authentication, authorization (role-based access control), and input validation
• Design and evolve PostgreSQL database schemas using Flyway migrations, including JSONB modeling for flexible domain objects
• Develop responsive, accessible UI components following existing design patterns and component libraries
• Integrate with third-party advertising platform APIs (Google Ads, Meta Marketing API, Adform) for account management and data synchronization
• Implement and maintain OAuth flows for external platform connections
• Build complex business logic including billing calculations, invoice generation, and payment processing workflows
• Write efficient database queries and optimize application performance for large datasets
• Collaborate with the data engineering team on Snowflake integrations for analytics and reporting features
• Participate in code reviews, providing constructive feedback and maintaining code quality standards
• Troubleshoot production issues across the full stack using AWS CloudWatch logs and application monitoring
• Contribute to CI/CD pipeline maintenance and deployment processes

Qualifications

Professional Competencies

• 4-6 years of professional software engineering experience in full-stack web development
• Strong proficiency in Java (11+) and Spring Boot, including Spring Security, Spring Data JPA, and RESTful API design
• Strong proficiency in React (16+) with TypeScript, including hooks, state management, and modern component patterns
• Solid experience with PostgreSQL including schema design, query optimization, indexing strategies, and migrations
• Experience with CSS frameworks (Tailwind CSS preferred) and building responsive layouts
• Familiarity with cloud services, particularly AWS (S3, SES, Lambda, ECS, CloudWatch)
• Experience integrating with third-party REST APIs and OAuth 2.0 authentication flows
• Understanding of Git workflows, pull request processes, and collaborative development practices
• Ability to independently own features from technical design through deployment
• Strong debugging skills across frontend and backend, including browser DevTools and server-side logging

Cultural Competencies

• Must be able to work primarily between the hours of 9:30 AM - 6:30 PM ET
• Must have a player/coach mentality, willing to both execute and lead
• Ability to juggle multiple projects concurrently and set and meet deadlines

• Skilled at receiving and providing direct feedback
• Collaborative mindset and great teamwork skills
• Entrepreneurial & adaptable; great learning skills
• Curious, research-minded, data-informed
• Able to search for possible solutions and apply them
• Creative confidence
• Proactive communicator
• A sense of humor and a love of online culture
• Thrives in a start-up culture