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Senior Software Engineer at Longtail-ai

Longtail-ai · Barcelona, Spain · Hybrid

Microsoft Excel

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About Longtail

At Longtail, we’re building an intelligent, autonomous decision-streaming platform for airlines. We combine scalable automation, proprietary algorithms, and contextual data to stream millions of real-time decisions directly into airline systems. Our platform lets airlines offer every possible travel product across their network—giving travelers more options on thousands of routes worldwide.

The Role

You’ll help shape how our decision systems evolve—balancing the realities of a four-year-old live product with the creation of entirely new ones. You’ll design and build systems from scratch while guiding how existing ones scale and improve.

As one of the founding engineers in our new Barcelona tech base, working closely with two of the founders, you’ll play a key role in defining technical culture, standards, and operating rhythm as the team grows.

This is a hands-on architectural role with real agency and end-to-end responsibility.


About LongtailAt Longtail, we’re building an intelligent, autonomous decision-streaming platform for airlines. We combine scalable automation, proprietary algorithms, and contextual data to stream millions of real-time decisions directly into airline systems. Our platform lets airlines offer every possible travel product across their network—giving travelers more options on thousands of routes worldwide.The RoleYou’ll help shape how our decision systems evolve—balancing the realities of a four-year-old live product with the creation of entirely new ones. You’ll design and build systems from scratch while guiding how existing ones scale and improve. As one of the founding engineers in our new Barcelona tech base, working closely with two of the founders, you’ll play a key role in defining technical culture, standards, and operating rhythm as the team grows. This is a hands-on architectural role with real agency and end-to-end responsibility.

In this role, you’ll
  • Design systems from scratch—defining architecture, interfaces, and data flows for new products.
  • Lead 0→1 technical initiatives—from concept to first release—across the core platform and new product lines.
  • Refactor and modernize existing components for scalability, reliability, and clarity.
  • Convert algorithms and decision logic into robust, modular, production-ready systems.
  • Build for observability and feedback; track and evolve system behavior after launch.
  • Identify and resolve structural edge cases at the architectural level.
  • Partner with product, business, and data teams to define how decisions become code.
  • Mentor engineers, set technical patterns, and raise design judgment across the team.


    • Who You Are
  • 8 + years of experience designing and scaling distributed systems.
  • Skilled at both creating new architectures and operating within complex existing ones.
  • Thrive in low-structure, high-ownership environments.
  • Strong architectural sense and deep curiosity about system behavior in production.
  • Translate analytical or algorithmic logic into scalable, observable systems.
  • Calm under ambiguity; create structure and direction where none exists.
  • Excellent communicator and mentor; lead through clarity and reasoning.


    • Why Join Us

    You’ll design and evolve the architecture that powers Longtail’s products.
    You’ll have the trust and responsibility to make consequential technical decisions and see them through in production.
    You’ll also be part of the founding engineering group in Barcelona—helping establish a new tech base and building systems that will serve as its foundation.
    If you’re driven by building lasting systems and guiding others through complexity, this role gives you that scope and responsibility.
    Apply Now

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