Full Stack Developer

JammTokyojapandevpublished 07/22/2026
Must-have:TypeScriptHTMLCSSReactSvelteTailwindGitAWSFrontendBackendFullstack
Nice-to-have:FinTech

Full-Stack Developer

About the Role

We're looking for a Full-Stack Developer who is excited to build scalable, resilient systems and elegant user experiences at an early-stage startup. You'll own features end-to-end — from design and architecture to implementation and refactoring — while balancing immediate delivery with long-term technical health.

This role is ideal for someone who thrives in a fast-paced environment, has a proactive mindset, and wants to shape both product and engineering foundations.

Responsibilities

  • Design and implement new features across frontend and backend.
  • Architect systems thoughtfully (DB schema, internal communication, data flows) to enable feature scalability and robustness.
  • Take ownership of delivering individual features end-to-end.
  • Monitor tech debt and drive proactive refactoring.
  • Make smart trade-offs between speed and scalability when implementing features.
  • Continuously refine systems to support future growth.

Requirements

Must-Haves

  • Full-stack development capability (even if frontend-leaning).
  • If experienced, at least 2 years tenure at a single organization is preferred.
  • History of internal promotion is strongly preferred.
  • Proactive in identifying problems before they occur and taking action.
  • High intrinsic intelligence with the ability to make sound short-term and long-term technical decisions.

Preferred Qualifications

  • Excitement about working in an early-stage startup .
  • Curiosity and enthusiasm for new technologies .
  • Experience in the fintech/payments space is a plus.
  • Hands-on experience with some of the following:

Frontend Stack

  • HTML/CSS
  • Tailwind
  • Svelte / SvelteKit
  • React
  • TypeScript

Backend & Infrastructure Stack

  • Go (Chi)
  • ConnectRPC/gRRC
  • Protobuf / Bufbuild
  • Temporal
  • AWS
  • Terraform
  • Git / GitHub
  • PostgreSQL

Why Join Us?

  • Impact from day one : Shape the foundations of both product and engineering.
  • Growth opportunities : Be part of a small, ambitious team where your contributions are recognized.
  • Challenging problems : Work on complex systems that require thoughtful design and proactive innovation.
  • Culture of ownership : We value people who take initiative and push boundaries.