
Celsus Engineering AB · Sweden
Description Build the next-generation payment platform on a modern and future-proof tech stack. Working in a cross-functional team What we’re looking for Prove...
Description
Build the next-generation payment platform on a modern and future-proof tech stack. Working in a cross-functional team
What we’re looking for
Proven ability to design, optimize, and operate data-intensive systems, including schema design, performance tuning, and production troubleshooting in MS SQL Server–based environments.
Deep understanding of database performance and reliability, including indexing strategies, query optimisation, and handling production issues.
Experience building and operating backend services using .NET/C#, with a solid understanding of microservice architectures and distributed systems.
Experience designing and working with asynchronous messaging and event-driven systems, using Kafka, IBM MQ, or similar technologies.
Experience running services in containerised and orchestrated environments (Docker, Kubernetes/OpenShift), with awareness of scaling, resilience, and failure modes.
Experience contributing to or owning CI/CD pipelines for database changes and deployment automation, with a focus on safe, repeatable releases.
A collaborative engineering mindset, with a willingness to share knowledge, learn continuously, and improve how the team builds and runs software.
Meritorious with experience from financial services, payments, or other regulated environments.
Strong communication skills, with fluency in English; Swedish is a plus
About us We are champions of rail, inspired to build a greener, more sustainable future of travel. Trainline enables millions of travellers to find and book the best value tickets across carriers, fares, and journey options through our highly rated mobile app, website, and B2B partner channels. Great journeys start with Trainline 🚄 Now Europe’s number 1 downloaded rail app, with over 135 million monthly visits and £6.3 billion in annual ticket sales, we collaborate with 270+ rail and coach companies in over 40 countries. We want to create a world where travel is as simple, seamless, eco-friendly and affordable as it should be. Today, we're a FTSE 250 company driven by our incredible team of over 1,000 Trainliners from 50+ nationalities, based across London, Paris, Barcelona, Milan, Edinburgh and Madrid. With our focus on growth in the UK and Europe, now is the perfect time to join us on this high-speed journey. Introducing the Backend teams at Trainline👋 The Backend teams at Trainline build the core of Trainline’s world class product. We create the journey search functionality that millions of our customers use on a daily basis, the eCommerce platform that provides a secure and seamless experience and we connect Trainline to over 270 travel operating companies, across 45 countries in Europe and the rest of the world. Each team has a targeted domain focus, ranging between customer accounts and notifications, journey search, bookings, payments, carriers’ integrations, real-time timetable information, and much more. As a Senior .NET Engineer at Trainline you will...🚄 * Deliver new functionality or features, using the most appropriate tools & techniques * Ensure quality is at the heart of everything you and your team do * Continuously improve the code base * Keep our customer as the number one priority * Actively identify blockers, boulders, time sinks and waste, and actively attempt to remove them * Make significant contribution to technical decisions * Act as a coach and mentor to others in the team * Take full ownership of the development lifecycle from code to production, including deployment and monitoring Our Tech Stack 🔑 * Languages & Frameworks: C# (.NET 6–10) * Databases: DynamoDB, PostgreSQL * Cloud & Infrastructure: AWS Cloud, Docker, Terraform * CI/CD & DevOps: GitHub Actions * Monitoring & Logging: New Relic, ELK Stack We'd love to hear from you if you have...🔍 * Experience mentoring less experienced engineers and comfortable pair-programming with colleagues * Hands on experience with C# .NET and the latest features * Experience collaborating with front-end engineers and other disciplines to deliver end-to-end features and cross-functional epics * Experience working with identity and authentication systems (e.g. IdentityServer, OpenID Connect, OAuth2) * Experience designing and maintaining CI/CD pipelines (e.g. GitHub Actions, TeamCity, Spacelift or similar tools) * Experience with cloud platforms (AWS preferred; Azure or GCP also valuable) * Hands-on experience with Infrastructure as Code, particularly Terraform * Strong experience with observability practices (logging, monitoring, alerting) * Familiarity with tools such as New Relic and ELK stack (or equivalents) * Curiosity about AI and emerging tools * Experience supporting production systems and improving reliability * Strong experience building and operating microservices architectures * Experience with event-driven systems and asynchronous messaging patterns * Solid understanding of distributed systems and scalability challenges * Have excellent communication skills More information: Enjoy fantastic perks like private healthcare & dental insurance, a generous work from abroad policy, 2-for-1 share purchase plans, an EV Scheme to further reduce carbon emissions, extra festive time off, and excellent family-friendly benefits. We prioritise career growth with clear career paths, transparent pay bands, personal learning budgets, and regular learning days. Jump on board and supercharge your career from day one! We're operating a hybrid model and ask that Trainliners work from the office a minimum of 60% of their time over a 12-week period. We also have a 28-day Work from Abroad policy. Our values represent the things that matter most to us and what we live and breathe everyday, in everything we do: * 💭 Think Big - We're building the future of rail * ✔️ Own It - We focus on every customer, partner and journey * 🤝 Travel Together - We're one team * ♻️ Do Good - We make a positive impact We know that having a diverse team makes us better and helps us succeed. And we mean all forms of diversity - gender, ethnicity, sexuality, disability, nationality and diversity of thought. That's why we're committed to creating inclusive places to work, where everyone belongs and differences are valued and celebrated. Interested in finding out more about what it's like to work at Trainline? Why not check us out on LinkedIn, Instagram and Glassdoor!
About us We are champions of rail, inspired to build a greener, more sustainable future of travel. Trainline enables millions of travellers to find and book the best value tickets across carriers, fares, and journey options through our highly rated mobile app, website, and B2B partner channels. Great journeys start with Trainline 🚄 Now Europe’s number 1 downloaded rail app, with over 135 million monthly visits and £6.3 billion in annual ticket sales, we collaborate with 270+ rail and coach companies in over 40 countries. We want to create a world where travel is as simple, seamless, eco-friendly and affordable as it should be. Today, we're a FTSE 250 company driven by our incredible team of over 1,000 Trainliners from 50+ nationalities, based across London, Paris, Barcelona, Milan, Edinburgh and Madrid. With our focus on growth in the UK and Europe, now is the perfect time to join us on this high-speed journey. Introducing the Backend teams at Trainline👋 The Backend teams at Trainline build the core of Trainline’s world class product. We create the journey search functionality that millions of our customers use on a daily basis, the eCommerce platform that provides a secure and seamless experience and we connect Trainline to over 270 travel operating companies, across 45 countries in Europe and the rest of the world. Each team has a targeted domain focus, ranging between journey search, fares calculation, bookings, fulfilment, payments, refunds, carriers’ integrations, real-time timetable information, journey disruptions and much more. As a senior level .NET Engineer at Trainline you will...🚄 * Deliver new functionality or features, using the most appropriate tools & techniques * Ensure quality is at the heart of everything you and your team do * Continuously improve the code base * Keep our customer as the number one priority * Actively identify blockers, boulders, time sinks and waste, and actively attempt to remove them * Make significant contribution to technical decisions * Act as a coach and mentor to others in the team * Take full ownership of the development lifecycle from code to production, including deployment and monitoring Our Tech Stack 🔑 * Languages & Frameworks: C# (.NET 6–10) * Databases: DynamoDB, PostgreSQL * Cloud & Infrastructure: AWS Cloud, Docker, Terraform * CI/CD & DevOps: GitHub Actions * Monitoring & Logging: New Relic, ELK Stack We'd love to hear from you if you have...🔍 * Experience mentoring less experienced engineers and comfortable pair-programming with colleagues * Hands on experience with C# .NET and the latest features * Experience collaborating with front-end engineers and other disciplines to deliver end-to-end features and cross-functional epics * Experience working with identity and authentication systems (e.g. IdentityServer, OpenID Connect, OAuth2) * Experience designing and maintaining CI/CD pipelines (e.g. GitHub Actions, TeamCity, Spacelift or similar tools) * Experience with cloud platforms (AWS preferred; Azure or GCP also valuable) * Hands-on experience with Infrastructure as Code, particularly Terraform * Strong experience with observability practices (logging, monitoring, alerting) * Familiarity with tools such as New Relic and ELK stack (or equivalents) * Curiosity about AI and emerging tools * Experience supporting production systems and improving reliability * Strong experience building and operating microservices architectures * Experience with event-driven systems and asynchronous messaging patterns * Solid understanding of distributed systems and scalability challenges * Have excellent communication skills More information: Enjoy fantastic perks like private healthcare & dental insurance, a generous work from abroad policy, 2-for-1 share purchase plans, an EV Scheme to further reduce carbon emissions, extra festive time off, and excellent family-friendly benefits. We prioritise career growth with clear career paths, transparent pay bands, personal learning budgets, and regular learning days. Jump on board and supercharge your career from day one! We're operating a hybrid model and ask that Trainliners work from the office a minimum of 60% of their time over a 12-week period. We also have a 28-day Work from Abroad policy. Our values represent the things that matter most to us and what we live and breathe everyday, in everything we do: * 💭 Think Big - We're building the future of rail * ✔️ Own It - We focus on every customer, partner and journey * 🤝 Travel Together - We're one team * ♻️ Do Good - We make a positive impact We know that having a diverse team makes us better and helps us succeed. And we mean all forms of diversity - gender, ethnicity, sexuality, disability, nationality and diversity of thought. That's why we're committed to creating inclusive places to work, where everyone belongs and differences are valued and celebrated. Interested in finding out more about what it's like to work at Trainline? Why not check us out on LinkedIn, Instagram and Glassdoor!
THE ROLE Our Development team in Malaga is growing and we are now looking for a Senior Backend Software Engineer to join! Our Campaigns & Rewards unit at Betsson Group ensures our customers come back for more. It’s all about loyalty. We provide a world class customer experience beyond the game play featuring Tournaments, Dynamic personalized campaigns and much more! You will be part of preparing our journey to containerization, increasing the scalability of our systems while also maintaining their high quality. To accommodate new requirements, we are constantly re-evaluating our systems design and working on exciting new features. WHAT YOU'LL DO: * Design and develop distributed backend services using .NET and event-driven architecture. * Collaborate with product and commercial teams to turn engagement ideas into scalable, maintainable, and user-friendly solutions. * Optimize our microservice ecosystem for performance, reliability, and observability. * Drive our containerization and cloud migration strategy forward. * Participate in architecture discussions and help shape technical decisions. * For senior engineers: Lead architectural decisions and proactively identify areas for improvement. * Write maintainable, well-tested code and conduct code reviews. * Participate in incident resolution and the team’s on-call rotation. * Maintain clear technical documentation such as ADRs, runbooks, and guidelines. * Build and share your domain expertise within the team. WHAT TECH STACK YOU'LL BE WORKING WITH: We don’t expect you to know everything listed below – but the more you’re familiar with, the better. What matters most is your ability to learn, collaborate, and write high-quality, maintainable code. CORE TECHNOLOGIES These are essential to the role, and we’re looking for solid experience here – especially for senior candidates. * Languages & Frameworks: C#, .NET (modern versions after .NET Core) * Databases: SQL Server, PostgreSQL, Redis, Couchbase (experience with relational or document databases, including indexing and query optimization, is a strong plus) * Cloud & Containers: AWS, Kubernetes, Docker (experience with any major cloud provider or containerization platform is valuable) * Testing & Quality: xUnit/NUnit, mocking frameworks, k6 for load testing (understanding of unit, integration, and performance testing is more important than specific tools) ADDITIONAL TOOLS & PRACTICES Familiarity with these of similar tools and concepts is a plus. * Messaging & Microservices: Web APIs, Apache Kafka, RabbitMQ, Orleans (experience with any messaging or actor-based system is valuable) * Observability: Prometheus, Grafana, Loki, Splunk (or experience with other observability stacks) * CI/CD: GitHub Actions, trunk-based development, progressive delivery (familiarity with continuous delivery pipelines and deployment strategies is more important than specific tooling) * Architecture: Domain-driven design, event sourcing, actor model, distributed systems at planet-scale * Ways of Working: Agile and Lean principles, DevOps mindset, strong collaboration WHAT WE OFFER * 25 working days of paid vacation. * Private health and life insurance. * Flexible compensation package for transport, meals, and more! * Hybrid work policy for the best of office and home. * Up to 10 days per year working remotely from abroad. * €300 yearly wellness allowance. * Office perks to make your day easier. * Referral program with a bonus for successful hires. * Intensive summer schedule in August for extra flexibility and work-life balance. We can also offer you an environment full of ambition and passion. One day is never like the other as the only constant is change, to the better, to the greater. We strive to be the best in whatever field we choose to play on, and we make sure to have fun along the way! CHALLENGE ACCEPTED? By submitting your application, you understand that your personal data will be processed as set out in our Privacy Policy