Mercari is Your Marketplace. We make it super easy to sell (or buy) almost anything. We all have things we don’t use, never used or simply outgrew. But that stuff still has value. Mercari gives you the power to simply sell it, ship it, and earn some cash for it. Fashion to toys. Sporting goods to electronics. All the brands you know and love. Our mission is simple: to make selling easier than buying. And with 50M+ downloads in the U.S. and almost 500k new listings every day, we're just getting started.

Our Engineers are developing complex software systems that scale to millions of users, all with production quality deployment, monitoring, and reliability.  You will be designing, developing, testing, deploying, maintaining, and improving our mission-critical backend systems. You bring an insatiable desire to build safe and secure systems that have a direct impact on users.  You love to solve complex performance problems and architectural challenges.  And you take great pride in mentoring and collaborating in an open, respectful, flexible, and empathic manner.

The Sr Software Engineer, Backend plays a key role in building and optimizing our marketplace platform's backend services. This role involves developing scalable, high-performance microservices, collaborating closely with product and frontend teams, and implementing best practices for modern backend development. This role requires deep expertise in Go, PHP, distributed systems, and microservices architecture.

What you’ll be doing:

• Lead the development of complex backend features and services, such as payment processing and inventory management systems
• Design and implement scalable backend architectures and patterns, including microservices and event-driven systems
• Drive technical decisions and best practices for backend development, including coding standards, performance budgets, and testing strategies
• Mentor and guide other engineers in backend development practices through code reviews and technical presentations
• Collaborate with product and frontend teams to define technical requirements and feasibility of new features
• Optimize backend performance and scalability, focusing on database optimization, caching strategies, and load balancing
• Contribute to backend platform technology and strategic roadmap decisions, including technology evaluation and technical debt reduction
• Lead technical discussions and architectural reviews for major features and system changes

What you’ll need:

• Bachelor's degree in Computer Science, Data Science, Engineering, or a related field (or equivalent experience)
• At least 8 years of experience in backend development
• Experience with large-scale distributed systems handling millions of users
• Experience with microservices architecture and service mesh
• Experience with performance optimization at scale, including database optimization and caching strategies
• Experience with modern backend build tools and deployment strategies (Docker, Kubernetes, Terraform)
• Expert knowledge of Go and PHP ecosystems
• Deep understanding of backend performance optimization techniques
• Strong architectural and system design skills
• Excellent knowledge of Agentic AI tools and workflows
• Excellent mentoring and technical leadership abilities

This position is based in the San Francisco Bay Area with an expectation of in-office (Palo Alto) 2-3 days per week.

The applicable salary range for this role is $168,000 to $252,000 for applicants located in the San Francisco Bay Area.

Why Mercari:

Small enough to make an impact, but established enough to provide the stability you need to be successful, Mercari is the best of both worlds. At Mercari you are encouraged to take risks. And when you do, you can do it confidently, knowing you have a team and a company that supports you.

As we grow, your career opportunities with Mercari grow. As our teams expand, your responsibilities expand. Our teams are supported with access to new tools, technologies, and learning opportunities.  We will never stop growing.

Total Rewards:

• Flexibility: Work from home and the office, depending on need and receive flexible time off  
• Wellbeing: Top-notch insurance plans, best-in-class new parent offerings and access to mind and body wellness apps
• Growth: As we grow, your career opportunities grow, we provide access to new tools, technologies and learning opportunities
• Comprehensive and total rewards: We provide a strong financial foundation and rewards that go beyond the paycheck
• Teamwork: We are each other's biggest fans- we celebrate from virtual coffee breaks to recognition programs