Backend Product Engineer TL;DRWe’re a global e-invoicing platform operating in 25+ countries.Revenue grew 10x last year, and we plan to 3x in 2026.Role: own integrations end-to-end — research, define, build, ship, and iterate with customers.Looking for: 1–10 years of backend experience, builder mentality, fluent English, comfort with ambiguity, and complex domains.Compensation: €50k–€90k base + Stock Options.Location: Madrid (at least 3 days/week in our beautiful office in El Viso, Madrid).⸻Hi there 👋🏼,I’m Juan, the CEO of Invopop. We help companies like Fever, DeepL, Booksy, and SumUp issue and receive invoices that comply with local requirements across 25+ countries.We're looking for a Backend Product Engineer to join our team in Madrid. If you enjoy solving challenging problems with elegant software solutions, owning your roadmap, and directly interacting with customers, this role could be a great fit!About InvopopInvopop helps global companies like SumUp, Fever, and DeepL issue and receive invoices across more than 25 countries through a single API.In the next five years, more than 40 countries, including the entire EU, will mandate that businesses send invoices electronically in XML format and report them in real time to tax authorities. This reduces fraud and enables companies to automate invoice processing instead of relying on OCR. There’s only one catch: each country has defined unique standards, forcing global companies to build dozens of local integrations—or integrate once with Invopop. :)Invopop was founded by Sam Lown, co-founder and former CTO of Cabify, and Juan Moliner (ex-BCG), based on Sam’s experience dealing with this problem at CabifyWe’ve raised €2.8M from top-tier venture capital firms, including YCombinator (W23), and have been named the Best Startup at South Summit 2024 and Madrid's Hottest Startup of 2024 by Wired.Your mission as a Backend Product EngineerWith Invopop, users build workflows by chaining Actions, each action being managed by an App. An App is a standalone service focused on a single goal, such as reporting an invoice to a tax authority, synchronizing it with an external system (e.g., ERP), or transforming/enriching a document.As a Staff Backend Product Engineer, you’ll be the owner of several Apps end-to-end, from the initial research to launching, and maintaining them in production:Investigate new countries and systems: read regulations and technical docs, turn ambiguity into clear requirements, and consult local experts when needed.Design and build integrations in Go on top of our modular architecture (NATS, CQRS patterns, Kubernetes on GCP).Make product decisions: what and how to build it, what to cut, and when to ship.Support customers using your Apps and iterate based on real feedback.Contribute to GOBL, our open-source standard for commercial documents.Who we’re looking forBackend engineering experience, ideally with Golang.Strong communication skills in English.Empathy for customers—you're eager to engage with clients and influence product decisions.Comfortable defining the scope as you build, learning new technologies, and navigating unfamiliar domains.Experience starting projects from scratch—perhaps as a founder, open-source contributor, or through impactful side projects.Compensation€50k–€90k base + Stock Options, depending on seniority level.If you have 10+ years of experience and are looking for a higher-leverage role (broader scope, leading multiple tracks), we’re also hiring for a Senior Product Backend Product Engineer (€90k–€140k base + ESOP).Where you’ll workWe’re in Madrid (Calle Guadalquivir, El Viso), 5 minutes from Nuevos Ministerios.No fixed schedule. We expect at least 3 days/week in the office — high-context work moves faster in person. Sam and I are often in the office, and part of our role is to be close to decisions and context.Why join InvopopReal ownership: you research, decide, build, ship, and support your own Apps.Work closely with Sam Lown (founding CTO of Cabify) and a small, high-bar team.Hyper-growth: 15 launches planned in 2026 and a 3x growth goal.Full room to experiment: leveraging AI to the infinite, switching frameworks, databases, schemas, nothing is set in stone here—as long as you can justify why.No bureaucracy or politics: product, taste, and ideas win over anything elseInterview processIntro call (30 min)Take-home exerciseTechnical interview (1h)Final interview, in person (1h)