Founding Software Engineer

Madrid, Spain / Portugal·Full-time·Added 3 months ago

The Flex

6 open roles

What they offer

  • Full-time hours

    Per the ad.

  • Fully remote

    Per the ad.

What they ask for

  • Have the right to work in Spain

    The Flex doesn't mention sponsorship in the ad.

  • Work in English

    English is required, per the ad.

  • Have senior-level experience

    Senior-level role.

This job was published 3 months ago

The role

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

Our mission is ambitious: 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 fragmented systems, and creating seamless experiences for guests, landlords, and operators across the world.

We're looking for a Founding Software Engineer to help architect and build the technology that powers the future of The Flex.

This is not a typical engineering role.

You'll work directly with the founder, influence product strategy, make architectural decisions, and build systems that become the foundation of a global business.

You'll have extraordinary ownership, responsibility, and impact from day one.

What you'll do

Design, build, and launch the software that powers bookings, pricing, payments, operations, communications, and guest experiences.

Make key technical decisions and help define the long-term architecture of Base360.ai.

Develop workflows and systems that automate operational processes across multiple countries and thousands of stays.

Build AI-powered tools, agents, and workflows that improve productivity, decision-making, and customer experience.

Develop and maintain integrations with platforms including Airbnb, Hostaway, Stripe, Twilio, Google, OpenAI, and other strategic partners.

Operate with urgency and ownership, turning ideas into production-ready solutions quickly and effectively.

How you'll work

Work from anywhere. We care about results, not hours.

What You'll Build

As a Founding Software Engineer, you'll help create and scale Base360.ai—the technology platform that powers every aspect of The Flex.

From AI-powered workflows and booking systems to operational automation and intelligent decision-making, you'll build products that directly impact revenue, efficiency, and customer experience.

You won't just ship features.

You'll create systems that replace manual work, unlock scale, and become a competitive advantage for the company.

Solve Real Problems

Work on challenges such as:

  • Reservation synchronization

  • Dynamic pricing

  • Smart access management

  • Guest communication automation

  • Operational forecasting

  • Maintenance and cleaning automation

  • AI-powered alerts and monitoring

  • Revenue optimization

Tech Stack

Our current stack includes:

  • Python

  • FastAPI

  • React

  • TypeScript

  • Supabase

  • PostgreSQL

  • AWS

  • OpenAI APIs

  • Stripe

  • Twilio

  • Docker

  • GitHub Actions

We care more about your ability to learn and build than your experience with any specific technology.

What Success Looks Like

Within your first year:

  • Critical company operations are automated through systems you've built

  • Base360.ai becomes a core competitive advantage

  • New products are shipped rapidly and reliably

  • Engineering velocity increases significantly

  • AI-powered workflows are embedded across the business

  • The platform is ready to scale internationally

This Role Is Not For You If

  • You're looking for a predictable corporate environment

  • You prefer maintaining systems rather than building them

  • You need constant direction and supervision

  • You avoid ownership outside your immediate responsibilities

  • You are uncomfortable with change, ambiguity, and rapid execution

If you're excited by building products, solving hard problems, leveraging AI, and helping create the operating system for modern renting, we'd love to hear from you.

#LI-Remote

Requirements

What we're looking for

  • Strong software engineering fundamentals

  • Experience building production-grade applications

  • Strong understanding of APIs, databases, and system design

  • Product mindset and customer obsession

  • Ability to work independently with minimal supervision

  • Strong problem-solving ability

  • High level of ownership and accountability

Nice to have

  • Startup experience

  • Experience with AI products or LLM integrations

  • Experience building SaaS products

  • Experience with FastAPI, React, AWS, or Supabase

  • Marketplace, travel, or PropTech experience

Pay & benefits

What you'll get

Your work will directly shape how thousands of people live, travel, and experience cities.

You'll have significant influence over product, technology, and company direction.

Work closely with leadership and help define the future of the business.

Gain exposure to engineering, AI, product, operations, growth, and company-building.

Competitive compensation with meaningful upside for exceptional contributors.

About The Flex

The Flex is a PropTech company operating in the real estate technology sector, focused on building software solutions for the property industry. The company is at an early stage, operating as a startup with a small, focused team. Their work centers on developing products that address challenges in the real estate market, leveraging technology to improve processes for property professionals.

The Flex has established a presence in Madrid, Spain, where they are actively hiring for their founding team. As a young startup, they offer international professionals the opportunity to join at the ground level, taking on significant ownership and responsibility in shaping the company's product and growth. Their work culture is likely dynamic and fast-paced, typical of early-stage startups, with a strong emphasis on engineering and product development.

Industry
PropTech
Employees
50
Headquarters
Madrid, Spain
In Spain
Madrid

Good to know if you are moving

  • Early-stage startup: joining now means you can have significant impact on the product and company culture.
  • Based in Madrid, Spain, offering a chance to be part of a founding team in the PropTech sector.
  • As a startup, the company may offer equity or other incentives to early employees, common in this stage of company growth.
  • The team is small, so roles are likely to be cross-functional and offer broad responsibility.
  • The company is building software for the real estate industry, a sector with global relevance.

In their own words

About the company & team

As one of the first engineers, your influence will extend beyond code. You'll help shape processes, culture, product direction, and the future engineering team.

All open roles at The Flex
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