Full-Stack Builder

About the role

About Katapult Labs

Katapult is an AI-first engineering studio connecting senior LATAM talent with startups and companies in the US. We're not a staff-augmentation shop: every person we put in front of a client represents Katapult, co-creates product, and owns the outcome directly, with no managers or leads acting as a layer in between.

The Role

We're looking for a Full-Stack Builder to join the founding technical team behind one of our partners, an early-stage product with big ambitions to become a real tech company: web platform, mobile app, and everything in between. Our partner already has a first version of their site live, built by a non-technical founding team full of product ideas. We need someone who can step in, understand and harden the existing architecture, refactor where needed, and help seed the technical process for building product going forward.

This is a builder role, not a heavy-architecture or platform-engineering seat. You'll move fast, ship with sufficient quality, and work closely with a product-minded team that cares deeply about user experience and engagement. Mobile development isn't required from day one, but the team expects to build a mobile app down the line, so comfort picking that up matters. If the engagement goes well, this grows into a two-builder team supporting the full platform.

KEY RESPONSIBILITIES

- Understand and evaluate the current architecture of our partner's existing web platform

- Refactor and harden the codebase to support rapid, reliable iteration

- Build new features end-to-end, working closely with the product lead on UX and engagement-focused functionality

- Help establish lightweight technical processes (code review, deployment, documentation) as the team scales

- Collaborate directly with a technical product manager and design lead in a fast-moving, startup environment

- Be ready to extend work into mobile development as the product roadmap evolves

REQUIREMENTS

- Advanced conversational English, since all collaboration happens in English

- Strong full-stack engineering experience with modern web technologies (frontend and backend)

- Demonstrated ability to work as a builder: shipping fast, with just enough architecture, not over-engineering

- Comfort working directly with founders and non-technical stakeholders, translating product vision into working software

- Experience refactoring or hardening an existing early-stage codebase

- Product analytics tooling (Amplitude, PostHog, or similar)

- Agentic mindset: comfortable using AI coding tools (Cursor, Claude Code, etc.) as part of daily workflow

- Strong communication skills, comfortable asking clarifying questions and flagging blockers early

NICE TO HAVE

- Prior experience building consumer-facing (B2C) products with high user engagement