Staff 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: 10+ years of backend experience, strong product judgment, fluent English, builder mentality, comfort with ambiguity, and complex domains.Compensation: €90k–€140k base + Stock Options.Location: Madrid (at least 3-4 days/month in our office, travel expenses paid).⸻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 Staff Backend Product Engineer to join our team. If you enjoy solving hard problems with elegant software, owning your roadmap, and helping shape what we build (and how), 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, based on his experience dealing with this problem at Cabify.We’ve raised €2.8M from top-tier global VC 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 Staff 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 maintaining 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).Drive product decisions: define what “good” looks like, choose trade-offs, cut scope when needed, and ship.Support customers using your Apps and iterate based on real feedback.Raise the bar across the team: review PRs, mentor engineers, and influence product and technical direction (architecture, patterns, qualityWho we’re looking for10+ years building backend systems (APIs, distributed systems, or complex domains). Golang is a plus, but not required.Fluent English: it's our internal working language.Strong product judgment: you can scope, prioritize features, and make trade-offs under ambiguity.Customer empathy: you’re comfortable speaking with customers and translating feedback into product decisions.A track record of high-agency: you’ve led projects end-to-end, improved systems over time, and made teams faster through reviews, standards, and mentorship.Compensation€90k–€140k base + Stock Options, depending on seniority level.Where you’ll workWe’re based in Madrid (Calle Guadalquivir, El Viso), 5 minutes from Nuevos Ministerios.We genuinely enjoy working in the office, and right now the team benefits significantly from high-context, fast decision-making in person. So our default is Madrid-based.That said, for a truly exceptional engineer who can operate independently, we can be flexible, as long as you can commit to coming to the Madrid office 3–4 days per month. We’ll cover travel expenses.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: frameworks, databases, schemas, AI tools — nothing is sacred, as long as you can justify the choice.No politics: product, taste, and good ideas win.Interview processIntro call (30 min)Take-home exercise (optional)Technical interview (1h)Final interview, in person (1h)