Senior Backend Engineer (f/m/d)

WeHireYou; Warsaw (IN); On-site; USD 55,000 - 83,000; Full time

Benefits offered by this job

Top compensation including equity

Work from abroad - 20 days

Learning & Development budget

Job summary

Moss is seeking a Senior Backend Engineer to join our Warsaw team, driving backend development across multiple squads and collaborating with PMs, designers and frontend engineers to deliver robust APIs and scalable services.

Required are strong Java and Spring skills, microservices architecture, REST APIs, testing practices, and fluent English. This is a hands-on, impact-driven role in a fast-growing SaaS scale-up with equity and international exposure.

Qualifications

• Proven Backend Engineer with end-to-end project ownership.
• Strong Java and Spring experience, with microservices and message queues.
• REST API design and testing expertise, including unit/integration tests.
• Fluent English and collaborative mindset.

Responsibilities

• Lead backend development aligned with product requirements and performance goals.
• Collaborate with PMs and designers during kick-offs to refine architecture.
• Define APIs and ensure smooth integration with frontend teams.
• Write reliable, well-tested code and end-to-end tests.
• Support rollout strategies and monitor performance post-release.

Skills

Java

Spring

Microservices

REST API

Testing

English

Tools

CI/CD pipelines

Docker

Kubernetes

Job description

Senior Backend Engineer (f/m/d)

At Moss, we give finance professionals the power to automate their day-to-day and make forward-thinking decisions.Our team and culture make us unique — we’re driven by impact and growth, where every one of us strives to learn and excel. Recognised by Sifted’s Rising 100 and LinkedIn's Top Startups, we’re here to help propel your career and together, make Moss a lasting success.

Our Engineering teams are seeking Senior Backend Engineers (f/m/d) for a variety teams in Warsaw. The following teams have open positions:

• Sales Enablement
• Pricing & Billing
• Acquisition
• Spend Management
• Activation & Card Spend

Collaborating closely with designers, product managers and frontend engineers, you will bring innovative ideas to life, ensuring our product helps business automate and simplify everyday tasks with intuitive and efficient tools.

Your responsibilities

Here’s a bit more on what you can expect to be doing day-to-day:

• Backend Development: Lead the development of the application, ensuring it aligns with the product requirements and meets performance and usability standards. Proactively provide regular updates on work progress, achievements and challenges to product managers (PMs) and designers.
• Collaborative Planning: Partner with PMs and designers during project kick-offs to gain a comprehensive understanding of the overall vision, user needs, and goals. Provide valuable insights to refine UI/UX concepts and contribute to the planning of backend development.
• Frontend Collaboration: Collaborate closely with frontend engineers to determine required APIs and frontend functionality. Maintain clear communication channels to ensure smooth integration of frontend and backend components.
• Testing and Quality Assurance: Produce well tested and reliable code. Writing unit and functional (end-to-end) tests.
• Rollout and Performance Monitoring: Collaborate with product managers to devise efficient rollout strategies for new features. Monitor performance and user feedback to identify areas for improvement and proactively address potential issues.

About you

We think you’ll need the following experience and qualifications to succeed in this role:

• Proven experience as a Backend Engineer, leading projects end-to-end to launch.
• Proficiency in Java development technologies (incl. Spring framework), as well as latest features and best practices such as microservices, message queue, alerting, reliability and feature flags.
• Understanding of development design patterns and techniques, incl. Rest API design principles.
• Hands-on experience with testing approaches and libraries (unit testing, integration testing).
• You are fluent in English.

In addition, here are the skills and attributes we are looking for:

• Pragmatic Tech Enthusiast: You have the theoretical and practical background to engineer our product. You pursue quality and scalability and follow industry and company best practices. You build systems that are easy to maintain and to understand by others.
• Delivery Focused: You understand and focus on what is important to deliver the most impact. This means accurate development and delivery estimations, ruthless prioritization and saying no to less important things. You are driven to deliver tangible outcomes within estimated timelines, and you swiftly tackle challenges, and provide clear direction to others.
• Collaborative Communicator: You convey information effectively to a variety of audiences, and actively participate in daily meetings, keeping others informed about your progress and status. You’re able to form trustworthy connections by creating and maintaining open communication with colleagues throughout the development process.
• Inquisitive Mindset: You’re detail-oriented and seek to develop a deep domain knowledge by proactively seeking to understand workflows and technical intricacies. You’re curious and unafraid to question assumptions and propose alternative approaches, ensuring the product is tailored to meet customer needs.
• Team Player: You bring a team together to work towards a shared goal, as well as support individuals throughout all phases of a project.

About Moss

Moss is a SaaS scale-up founded in Berlin, with a team of 300+ people from 50+ nationalities in 5 offices across Europe. Our ambition is bold: to power every SMB’s spend across Europe - fully digital, AI-driven, and seamlessly integrated for complete control. To date, over 5000 businesses in Germany, Netherlands and the UK use Moss’ leading spend management product, with modules such as corporate cards, accounts payables, employee cash reimbursements and procurement. Moss has raised a total of €180 million in funding and is backed by the most renowned tech investors including Valar Ventures, Tiger Global, Global Founders Capital, Cherry Ventures and A-Star.

Be part of a culture that thrives on impact and speed, where you can take bold moves, learn fast and accomplish more. We’re a place where you can fast track your career - here's what else to expect:

• Top-of-market compensation package, including equity.
• Our vibrant offices are at the heart of our culture, where in-person time fuels collaboration and connection over weekly breakfasts and Friday demos.
• Additional benefits include: 20 days “work from abroad”, 600EUR/GBP Learning & Development Budget, and other local benefits.

Unless stated otherwise, benefits apply to full-time positions (interns and working students receive a tailored package).

Warsaw