Summary: Seeking a Senior Software Engineer to own critical backend billing systems, designing and evolving the Quote-to-Cash stack for a fast-growing Finance platform. Highlights: 1. Own critical backend systems for subscription, billing, and monetization flows 2. Collaborate with Product, Finance, Sales, and Data teams on monetization 3. Drive platform evolution and migrations, mentoring less-experienced engineers Hello! Would you love to improve the way companies take care of their people, their most valuable asset? Senior Software Engineer – Billing Systems **DataOps / Billing Systems:** What’s the mission? * Factorial is building a world\-class Finance platform to support how customers subscribe, upgrade, and grow with us. * As a Senior Software Engineer, you’ll own critical backend systems that power our subscription, billing, and monetization flows—systems where correctness, auditability, and reliability are non\-negotiable. * You’ll design and evolve our Quote\-to\-Cash stack, integrating with platforms like Dealhub, Stripe, Chargebee (or equivalents), and internal systems to ensure scalable, compliant, and data\-consistent billing operations. The role * You’ll be part of a fast\-growing Engineering team of 250\+ product developers, owning high\-impact systems that directly affect revenue, customer experience, and operational efficiency. * You will design and build backend services and APIs for subscription lifecycle management (plan changes, upgrades/downgrades, credits, refunds, invoicing), and define clean boundaries that enable smooth integrations with internal platforms (customer\-facing portals, backoffice tools, ERP/CRM). * You’ll collaborate closely with Product, Finance, Sales, and Data teams to translate monetization requirements into robust technical solutions—balancing speed, correctness, and long\-term maintainability. * You’ll take end\-to\-end ownership: from architecture and implementation to production operations, monitoring, reconciliation mechanisms, and continuous improvement. Our stack \& the day\-to\-day * We predominantly use Ruby on Rails for the backend and React/React Native for clients, but you’ll also have the opportunity to dive into Scala, Python, or any language best suited to build high\-performance finance data services. * You’ll design production\-grade APIs and event\-driven workflows for billing operations, supporting asynchronous processes and integrations across multiple systems. * You’ll implement monitoring, alerting, and data integrity controls (reconciliation, audit logs, consistency checks) to detect and mitigate issues in payment flows and synchronization. * You’ll drive platform evolution and migrations: evaluating third\-party providers, designing incremental migration strategies, validating data, planning rollbacks, and executing post\-migration verification. * You’ll write RFCs, join in technical conversations, and share knowledge while mentoring less\-experienced engineers. * You’ll iterate in short development cycles, running ephemeral dev environments to test and fail fast, all under a GitOps\-driven mindset with CI/CD best practices. Your first steps at Factorial * Read a lot: Get to know Factorial’s product, customers, and current Billing and monetization flows. * Learn a lot: Pair with team members from different domains (Finance, Data, Product, Engineering) to understand the Quote\-to\-Cash landscape and where we need stronger systems. * Code a lot: Contribute to quick wins in billing workflows and integrations—improving robustness, test coverage, and operational tooling. * Fail a lot: We encourage experimentation. We understand that trying out new ideas, failing, and improving is part of the role. * Talk a lot: Participate in team rituals and stakeholder sessions to ensure what we build is accurate, auditable, and solves real business needs. What we'd love to see in your background * 3\+ years of experience as a Software Engineer working on backend or platform systems. * Solid experience designing and maintaining production\-grade APIs and backend services. * Proven ability to work with complex domain logic and data\-sensitive systems, with a strong focus on correctness and long\-term maintainability. * Experience owning systems end\-to\-end, including production support, monitoring, and operational responsibility. * Strong plus: experience with subscription platforms, recurring billing, payments, invoicing, or monetization systems. * Strong plus: experience integrating with third\-party billing/payment providers (Stripe, Chargebee, or similar) and/or ERP/CRM systems. * Experience with event\-driven systems, asynchronous workflows, and system integration patterns. * Experience executing production migrations (including coexistence strategies), with validation, rollback planning, and post\-migration verification. * A strong ownership mindset, ability to navigate ambiguity, and clear communication with both technical and non\-technical stakeholders. * Comfortable working in English and with distributed teams. The hiring process * First conversation with a Manager: a mix of human and technical topics, focused on how we can work together, to align expectations and review our Engineering Rubrics (check them out: they’re open!) and salary range. * Tech interview with Factorial engineers, discussing a piece of code you’re proud of (or a mini\-challenge). We want to see how you solve problems, not just lines of code. * Final coffee\-chat with our Director of Data to deep\-dive into Factorial’s culture, vision, and answer any questions you might have. * All interviews are remote, using video conferencing tools! About us At Factorial, we’re building the leading business management software for companies of all sizes. Our platform centralizes key workflows across HR, finance, and operations, freeing teams from manual processes so they can focus on what really matters: leading, growing, and taking care of their people. With over 1,200 employees across 7 markets, we serve 700,000\+ users and are one of Europe’s fastest\-growing SaaS companies, backed by top\-tier investors and proudly headquartered in Barcelona.We believe in bold goals, radical ownership, and inclusive collaboration. If you're excited to shape the future of business management technology, we’d love to meet you. Our Values * We own it: We take responsibility for every project. We make decisions, not excuses. * We learn and teach: We're dedicated to learning something new every day and, above all, share it. * We partner: Every decision is a team decision. We trust each other. * We grow fast: We act fast. We think that the worst mistake is not learning from them. How We Work We follow an office\-first, flexible approach (80%\-20%) because we believe the best products are built when people collaborate face\-to\-face. We work on\-site several days a week in our Barcelona HQ (or Madrid office) to connect, brainstorm, and ship together, while keeping flexibility for deep work and personal balance. Perks of being part of our team We care about people and we also offer a lot of benefits for employees: * High growth, multicultural and friendly environment * Alan private health insurance * Healthy life with Wellhub (Gyms, pools, outdoor classes) * Save expenses with Cobee * Language classes * Breakfast in the office and organic fruit * Nora discounts * Free caffeine and theine * Pet Friendly Wanna learn more about us? Check our website!