Backend Engineer (Freelance)

About CardNexus CardNexus is building the ultimate platform for the Trading Card Game (TCG) community. Designed for players, collectors, investors, and game stores, we simplify collection management, provide real-time market insights, and streamline trading through smart matching technology. Our all-in-one solution bridges the gaps between fragmented tools and outdated systems, enabling users to value, trade, and grow their collections efficiently. Founded in 2024 by a team of repeat entrepreneurs and lifelong TCG enthusiasts , CardNexus brings together deep expertise in technology, product design, and competitive trading card games . We’re on a mission to redefine how millions of TCG fans engage with their collections —from streamlining inventory to optimizing trades and building a thriving community. If you’re passionate about TCGs and want to shape the future of the industry , we’d love to have you on board! Role overview We are hiring a Freelance backend engineer to join us immediately to tackle our most important projects, including but not limited to : Inventory management Import and export systems Deployment and industrialization (Logging, monitoring, observability, scalability) Perforrmance (API, Mongo database, etc.) You will work with our CPO, CTO, and two founding engineers. What You’ll Do As a Senior Backend Engineer, you will take full ownership of backend architecture, from problem definition to implementation and optimization. You will be responsible for delivering high-performance, scalable solutions for a high-traffic marketplace , ensuring every feature is built with efficiency, resilience, and maintainability in mind. Over the next 24 months, you will: Deliver Complex Features : Lead the implementation of intricate features such as: Real-time card scanning, inventory management, and trade matching . A scalable inventory system capable of handling large user collections efficiently. Integration of a Payment Service Provider (PSP) and user wallet system , ensuring secure transactions and seamless payment processing. Performance and cost optimization at all levels, ensuring minimal resource usage while maintaining high speed. Infrastructure scaling strategies to handle millions of daily requests reliably. Optimize for Performance and Cost Efficiency : Ensure that every piece of infrastructure and code is optimized for speed, resource efficiency, and minimal operational cost . Scale Infrastructure for High Traffic : Build robust logging, monitoring, and scaling strategies to handle millions of daily requests seamlessly. Ensure Security and Compliance : Implement rigorous security measures, including KYC processes, to protect users and maintain trust. Streamline CI/CD and DevOps : Enhance deployment pipelines for seamless integration and rapid iteration. Solve Broad and Deep Technical Challenges : Leverage your expertise across databases, cloud infrastructure, and backend technologies to deliver cutting-edge solutions. What You Bring Proven Track Record of Ownership : You take full accountability for projects, seeing them through from conception to delivery, ensuring high-quality results. Expertise in High-Traffic Systems : Experience designing and optimizing backends for large-scale, high-volume platforms with demanding performance requirements. Deep Database Mastery : Extensive hands-on experience with MongoDB , relational databases, and NoSQL solutions, with a strong ability to optimize queries and data structures for performance and scalability. Strong Backend Development Skills : Advanced proficiency in Node.js , TypeScript , and backend architecture. Broad Technical Knowledge : Comfort with cloud infrastructure (AWS, GCP), logging, monitoring, caching, and DevOps best practices. Efficiency-Driven Mindset : Ability to write clean, optimized code that minimizes execution time and resource consumption. Problem-Solving Excellence : Ability to decompose complex challenges into scalable, maintainable solutions with a performance-first approach. Fluent Communication : Strong written and spoken English skills, capable of articulating ideas clearly in a collaborative, fast-paced environment. Bonus Points: Experience working on a large-scale marketplace with high traffic. Expertise in MongoDB optimization and sharding strategies. Experience with frontend technologies like React, Next.js . Passion for Trading Card Games (TCGs) or gaming culture. What We Offer Fully Remote Work : Enjoy the freedom to work from anywhere with flexible hours that fit your lifestyle. Competitive Compensation : We offer a competitive salary that reflects your skills, expertise, and contributions. Professional Growth : Collaborate with a passionate team of TCG enthusiasts and tech experts to tackle cutting-edge challenges. Innovative Culture : Join a gamer-centric environment that celebrates creativity, gaming, and technology. Impactful Work : Play a key role in transforming the $15B TCG market with tools that truly make a difference for the community.