Senior Backend Developer

**3 reasons you should join our team** 1. You will work on systems that cannot go down. You design and maintain a high-availability platform that processes millions of secure transactions every day around the globe 2. You will go deep on backend craft. From creating and optimising microservices to levelling up database performance, you help build a backend known for accuracy, security, and long-term reliability 3. You will join a sharp and friendly engineering team. You collaborate with more than 30 experienced engineers, ship in agile teams, share knowledge, and solve complex payment challenges that actually matter Our offices are located in Delft, near Rotterdam. If you do not know Delft yet, it is one of the most loved cities among engineers, with beautiful canal-lined streets, good beers, a strong tech vibe, reasonable housing prices, a walkable centre that keeps life easy, and public transport that gets you anywhere fast. **Build the backbone of global e-commerce **What started as five people, a small office, and some orange nerf guns has grown into one of Europe’s fastest-growing fintechs. With 150+ colleagues, offices in Delft, Berlin, and London, and Worldline as our partner, we’ve got the perfect mix: the power of a global leader with the energy of a scale-up. At OPP, we build the technology that powers the next generation of e-commerce. From eBay Kleinanzeigen to IKEA, millions of users rely on our systems every day. We don’t just process payments, we enable platforms to accept, hold, and disburse funds securely. 24/7. **As Senior Backend Developer,** you contribute both strategically and hands-on. You work on the core of our platform: strengthening critical services, introducing cleaner architectures, and preparing our systems for new payment flows across Europe. You help us make smart choices about performance, reliability, and security, and you are comfortable dealing with the real-world complexity that comes with scale. With traffic rising across all regions, you help us stay fast and reliable under pressure and you guide teammates through complex engineering trade-offs. You do all this as part of one of our four agile Scrum teams focused on in-platform payments, onboarding, and core product innovation. You work with developers who know payments inside out and who tend to stay, because the work is meaningful and the team is strong. Our tech office sits in the city centre of Delft, a dedicated dev-only space for deep work with plenty of places nearby to grab a coffee or clear your head. **Some of the projects you’ll be part of** * Build new in-platform payment flows that move money in ways traditional e-commerce never had to. * Level up onboarding and compliance, making it faster for users and stricter where it counts. * Break big systems into clean microservices that stay fast when traffic hits across Europe and the UK. * Create the APIs and tools platforms need to grow without waiting on us. **Our tech stack** PHP, Laravel, Symfony, MySQL, Redis, Docker, Kubernetes, CI/CD.