Founding Software Engineer
Madrid, Spain / Portugal·Full-time·Added 3 months ago
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.
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