Senior Fullstack Engineer

Stack

Responsibilities

• ▹Lead the design and implementation of both backend systems and frontend interfaces
• ▹Proactively propose solutions and experiments instead of just flagging blockers
• ▹Translate complex business needs into elegant, scalable fullstack architecture
• ▹Advocate for code quality, security and performance across the entire repo
• ▹Continuously evaluate new technology (especially AI/LLM) to improve delivery
• ▹Contribute to open-source projects and internal AI research

Requirements

• ▹5+ years of experience building complex web applications
• ▹Strong proficiency in Python or Ruby
• ▹Mastery of a modern frontend framework
• ▹Solid understanding of SQL (PostgreSQL), CI/CD and cloud environments
• ▹AI-native workflow: using tools like Claude or Cursor to build faster
• ▹Fluent English (C1) for direct client collaboration

Soft skills

What we offer

• ▹Long-term, mission-driven engagements
• ▹Small teams (3-9 people) with real accountability and visibility
• ▹Mission-critical work for scaling and international brands
• ▹Real ownership of technology and implementation decisions
• ▹No micromanagement
• ▹Collaborative open-source and internal AI R&D
• ▹Growth through complex, direct client exposure

About the company

Upside partners with ambitious companies across the globe to solve complex, meaningful problems through technology, combining engineering, product thinking and design. Their latest open-source release is Enthusiast, a customizable agentic AI toolkit for e-commerce.