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 ship high-quality improvements.

You will:

• Build full-stack features across Ruby on Rails and Next.js
• Own product initiatives end-to-end, from identifying opportunities and shaping solutions through implementation, launch, and iteration.
• Partner with product/project managers and designers to identify customer pain points, uncover product opportunities, and deliver meaningful improvements.
• Use tools like Claude Code and Codex as a core part of your workflow to explore, develop, test, and ship
• Make practical technical decisions that balance speed, quality, maintainability, performance, and customer impact
• Build polished, reliable, easy-to-use experiences with strong attention to UX
• Use tools like Datadog and Mixpanel to monitor production behavior, investigate issues, 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
• Comfortable working across our stack, including Ruby on Rails, TypeScript, React, Next.js, MySQL/Postgres, Redis, MongoDB, Sidekiq, OpenSearch, AWS, and Docker
• Fluent with AI-assisted development tools such as Claude Code or Codex
• Proven at building and maintaining large-scale customer-facing web applications
• 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
• A strong partner to DevOps, with enough understanding of system architecture, cloud infrastructure (AWS), deployment, containerization, and infrastructure-as-code (Terraform) 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