At The Flex, we believe renting a home should be as simple as booking a ride.

Our mission is to enable anyone to live anywhere, anytime, without friction.

Powered by Base360.ai, our proprietary technology platform, we are building the operating system for modern renting—automating operations, connecting systems, and creating seamless experiences for guests, landlords, and operators worldwide.

We're looking for a Full‑Stack Product Engineer who thrives at the intersection of product, engineering, and execution.

This isn't a role where you'll simply implement tickets.

You'll identify problems, design solutions, build products, automate workflows, and help shape the future of the platform.

What You'll Do

Build Products End‑to‑End

— Take ideas from concept to production by designing, building, testing, and launching features that create measurable business impact.

Own Customer Problems

— Work directly with founders and operational teams to understand challenges and transform them into elegant software solutions.

Move Fast

— Ship quickly, gather feedback, iterate, and continuously improve products based on real‑world usage.

Create Automation

— Design systems that eliminate manual work and allow the company to scale efficiently.

Build Internal Tools

— Develop operational dashboards, workflow engines, management platforms, and AI‑powered tools used across the business.

Connect External Systems

— Build integrations with platforms such as Airbnb, Stripe, Hostaway, Twilio, Google, and OpenAI.

Leverage AI

— Implement AI‑powered features and workflows that improve productivity, decision‑making, and customer experience.

Scale the Platform

— Ensure systems remain reliable, secure, and scalable as the business grows internationally.

Tech Stack

Python

FastAPI

React

TypeScript

Supabase

PostgreSQL

AWS

OpenAI APIs

Stripe

Twilio





GitHub Actions

You don't need experience with every technology listed above, but you should be capable of learning quickly and adapting.

What We're Looking For Must-Have

Strong full‑stack development experience

Experience building production‑grade web applications

Strong understanding of APIs and databases

Product mindset and user‑centric thinking

Ability to work independently and take ownership

Strong problem‑solving skills

Excellent written communication

Nice‑to‑Have

Experience with FastAPI

Experience with React and TypeScript

Experience with AI tools or LLM integrations

Startup experience

PropTech, marketplace, or SaaS experience

What Success Looks Like Within Your First Year

You've launched multiple high‑impact features

Manual operational processes have been automated

Product development cycles are significantly faster

AI‑powered workflows have been deployed across the business

Base360.ai has become a stronger competitive advantage for The Flex

Why Join The Flex

Massive Ownership — You'll have direct influence over product decisions, architecture, and company strategy.

Build Real Products — Your work will impact thousands of users and properties across multiple countries.

Learn at Startup Speed — You'll work closely with founders and gain exposure to engineering, product, operations, AI, and business.

Remote‑First — Work from anywhere.

High Growth Environment — We're building quickly and looking for people who want to grow alongside the company.

This Role Is Not For You If

You prefer highly structured corporate environments

You only want to write code from predefined specifications

You avoid ownership outside your immediate responsibilities

You are uncomfortable moving quickly and adapting to change

If you love building products, solving real‑world problems, and creating systems that scale, we'd love to hear from you.

📌 Full-Stack Product Engineer (Madrid)
🏢 The Flex
📍 Madrid