Senior Full Stack Engineer

Sincere is looking for a Senior Full Stack Engineer to help us make our products meaningfully better. This is a high-ownership individual contributor role for a seasoned engineer who can take a broad product area, understand the customer and business needs, and turn those insights into polished, user-facing improvements.

Our primary application stack is Ruby on Rails and Next.js. We’re open to engineers with strong full-stack experience in Rails or closely related backend frameworks such as Django/Python, Laravel/PHP, or Phoenix/Elixir. We’re looking for engineers with deep React and Next.js experience and a strong track record of owning customer-facing product work across the full stack.

You will:

• Build and ship full-stack product features across Ruby on Rails and Next.js
• Own product initiatives end-to-end, from identifying opportunities and shaping solutions through implementation, launch, measurement, and iteration
• Build user-facing features and experiences that make our products more useful, intuitive, and enjoyable
• Partner closely with product/project managers and designers to understand customer pain points, evaluate opportunities, and determine what should be built
• Use Claude Code and Codex as a core part of your development workflow to explore codebases, develop solutions, test ideas, and ship efficiently
• Make practical technical decisions that balance speed, quality, maintainability, performance, and customer impact
• Work across the frontend and backend as needed, rather than being limited to one layer of the stack
• Use tools like Datadog and Mixpanel to understand production behavior, investigate issues, measure impact, and inform product decisions
• Champion new ideas and continuously look for ways to improve our products, engineering practices, and customer experience

You are:

• A seasoned full-stack engineer with 7+ years of professional software development experience
• Highly experienced with React and Next.js and comfortable owning customer-facing experiences from frontend through backend
• Experienced with Ruby on Rails or a closely related product-focused backend framework such as Django/Python, Laravel/PHP, or Phoenix/Elixir
• Fluent with AI-assisted development tools such as Claude Code or Codex and already use them meaningfully as part of your software development workflow
• Proven at building, launching, and improving large-scale customer-facing web applications
• Able to point to meaningful user-facing or visual product improvements you’ve helped shape and ship, not just improvements to the underlying code or architecture
• Product-minded, with strong instincts for customer needs, UX quality, business value, and technical tradeoffs
• A self-starter who brings structure to loosely defined problems and drives them through execution
• Comfortable working in a modern production environment that includes TypeScript, MySQL/Postgres, Redis, MongoDB, Sidekiq, OpenSearch, AWS, Docker, and related infrastructure
• A strong partner to DevOps, with enough understanding of system architecture, cloud infrastructure, deployment, containerization, and infrastructure-as-code to collaborate effectively
• Skilled at working in mature codebases, understanding existing architecture, and improving systems pragmatically
• Detail-oriented, with high standards for both the code and the customer experience
• Entrepreneurial, curious, and biased toward building, experimenting, and shipping
• Collaborative and low-ego, with strong communication skills and pride in your craft

Do you want to work at a growing company that invests in its team more than the average employer? Sincere is a family of brands with heart. The Company is home to Punchbowl®, Lovebird®, Timehop®, and Memento®, and builds technology that brings you closer and helps show you care to the people who matter the most. With Sincere Foundation, we support organizations that address basic needs, and envision a future where everyone has the opportunity to celebrate, recognize milestones, and honor memories. We provide a fun, casual, and innovative environment where hard work is recognized and rewarded.

What We Offer:

• 100% Health, Dental & Vision coverage
• 401K Plan with Profit Share
• Annual bonus potential
• Health & Wellness stipends
• Paid time off plus 12 paid holidays & Summer Fridays
• Paid parental leave
• Childcare benefits (dependent care FSA)
• Flexible, hybrid work environment
• In-person, all-expenses-paid Team Summits (2X a year)
  PLEASE NOTE: Our team is primarily based in Greater Boston. We will consider applicants who reside anywhere within a 2 hour drive of the city. While this role is remote, we have occasional in-person meetings at the office (every 4-6 weeks typically).
  The base salary range for this role is $120,000 - $160,000. Actual salary may vary based on skills and experience.