Senior PHP Backend Developer

About Shiftbase At Shiftbase, we build workforce software that helps people get work done. Thousands of teams across Europe rely on our platform every day to plan work, track time, and manage leave, freeing them from unnecessary admin so they can focus on what matters and what sparked their business. As we continue to grow in customers, usage and product ambition, the demands on our platform grow with us. Our backend needs to scale in quality, reliability and speed of change. That’s why we’re investing heavily in modernising our platform, building a foundation that allows us to move faster, deliver better experiences, and support the next phase of Shiftbase’s growth. About the role: As a Senior Backend Engineer, you are a key driver of both product delivery and platform modernisation. You work on the core of our backend, improving reliability, performance and scalability, with the explicit goal of turning Shiftbase from a platform people enjoy into a platform they love. You help evolve a mature monolithic codebase into a more modular, testable and future-proof architecture. By modernising the foundation of the product, you directly enable better user experiences, faster iteration and higher overall product quality. What you'll do Drive technical excellence Design and deliver high-quality, scalable solutions for complex features and system componentsMake informed architectural decisions that balance pragmatism with long-term visionSet the bar for technical craft through your contributions and code reviewsOwn complex technical initiatives from design through production, breaking them into testable increments Build for reliability and scale Define comprehensive testing strategies for complex features, championing quality within the teamDebug and resolve complex issues across multiple components, improving system observabilityApply security best practices throughout the development lifecycleContribute to monitoring, alerting and system health improvements Enable team growth Mentor engineers with targeted technical guidance and feedbackSupport onboarding and enable a collaborative, knowledge-sharing environmentHelp shape delivery practices and improve team velocity through data-informed decisions What we're looking for Core technical expertise You have deep backend engineering experience with complex, high-scale systems. We don't expect expertise in everything listed below. We value engineers who've built depth and breadth through genuine curiosity and a drive to solve real problems. These are examples of competencies that matter in this role: Modern PHP & architectural patterns: Experience with hexagonal architecture, domain-driven design, or similar patterns that emphasize domain modeling over framework magic. You can build maintainable systems without relying on framework shortcuts.SQL & database design: Comfort writing raw SQL (not just ORM abstractions) and working with complex relational schemas particularly around time-sensitive data like scheduling, timesheets and payroll where integrity and performance are critical.Legacy modernisation experience: You've gradually evolved mature systems rather than pursuing big-bang rewrites. You know when to modernize strategically vs. leaving working code untouched, and understand the balance between progress and stability when serving thousands of customers.Monolith to services: Experience breaking down monoliths with good judgment about when distribution solves real problems (deployment bottlenecks, team autonomy) vs. when it adds unnecessary complexity.Testing in legacy contexts: Practical experience with unit and integration testing, particularly incrementally improving coverage in existing systems. This might be your dream job if… ✅ You enjoy modernising a mature platform and turning legacy code into something you’re proud of ✅ You get energy from breaking down a monolith and shaping a more modular, service-oriented architecture ✅ You care about product quality, not just “shipping code”. ✅ You like improving reliability, performance and developer experience as much as adding new features ✅ You enjoy working closely with product and frontend to make better technical and product decisions This probably isn’t your dream job if… ⛔️ You only want to work on greenfield projects and avoid legacy systems altogether ⛔️ You’re uncomfortable refactoring existing code or making incremental improvements ⛔️ You prefer being handed fully-defined solutions rather than helping shape them ⛔️ You’re looking for a role where architecture decisions are already “done” ⛔️ You’d rather optimise locally than care about the end-to-end product experience Note: Candidates outside the Netherlands will not be considered