Moss

Develop backend applications, collaborate with product managers and frontend engineers, and ensure quality and performance. | Mid-level backend engineering experience with Java and Spring, strong collaboration and communication skills. | Mid-Level Backend Engineer 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 Mid-level Backend Engineers (f/m/d) for a variety of different 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). By applying for the above position, you will confirm that you have reviewed and agreed to our Data Privacy Policy.

Own and improve the stability, precision, and scale of production backend infrastructure for real-time AI retrieval systems. | 5+ years backend production experience with strong distributed systems fundamentals, monitoring, incident response, and cloud infrastructure knowledge. | We built Moss because Voice AI breaks when retrieval is slow. Most retrieval infrastructure was not built for real-time reasoning. It adds latency, breaks context mid-conversation, and becomes the bottleneck just as an AI product needs to feel instant. Moss is the real-time semantic search layer for conversational AI. We deliver sub-10ms retrieval directly in the browser, at the edge, on-device, or in the cloud, without making teams stitch together a slow retrieval stack. We are backed by YC and run in production for teams building serious AI products. Moss is deployed across 100+ countries, serves 1M+ voice minutes, supports enterprises serving 3,000+ of their own end customers, and has 350K+ package installs. The systems are already working at real scale. Now we are expanding the reliability, precision, and performance foundation needed for the next billion minutes. We are looking for a Senior or Staff Backend Engineer to own the stability, precision, and scale of our production infrastructure. This is not a greenfield role. You will work on live, high-throughput systems from day one: pushing latency lower, improving correctness, strengthening reliability, and helping Moss scale confidently with our customers. When milliseconds and correctness are both part of the product, your work defines the company. What You’ll Do Build and evolve the systems behind every Moss retrieval request: the query path, APIs, caching, indexing, and data plane that make sub-10ms retrieval possible. Take Moss from millions of real-time retrieval minutes to billions without letting latency, correctness, or reliability degrade along the way. Make sure retrieval is not just fast, but consistently right. Most of the work is dealing with messy customer data and figuring out why results are off when things don’t behave the way you expect. Find the bottlenecks before they become customer problems: traffic spikes, noisy workloads, bad cache behavior, broken edge cases, deployments, and everything that only shows up once a system is actually being used. Build the operational muscle around Moss: observability, load testing, deployment safety, alerting, incident response, and capacity planning. Work across our cloud and edge footprint - AWS, Cloudflare, Vercel, Supabase, Azure, GCP - and make strong technical calls on what belongs where as the product scales. Keep Moss enterprise-ready as we grow: secure data handling, access controls, auditability, and the production rigor behind SOC 2 and HIPAA. Work directly with customers pushing Moss the hardest. You will help debug real deployments, understand where systems break down, and turn those lessons into product and infrastructure improvements. Help define what “production-grade retrieval” means for Moss. Not just uptime, but how quickly we can ship, debug, scale, and earn trust from teams building their products on top of us. Core Stack Our core retrieval engine is built in Rust, with SDKs across TypeScript, Python, Swift, Android and other developer surfaces. The production stack spans cloud and edge infrastructure, including AWS, Cloudflare, Supabase, Vercel, Azure, and GCP. You do not need experience with every part of this on day one. What matters is strong judgment around systems design, performance, and operating infrastructure that customers depend on. Your First 90 Days On day one, you will ship code to production. In your first 30 days, you will get deep into the Moss query path and start taking ownership of the systems behind it - latency, correctness, caching, APIs, indexing, and the production infrastructure customers touch every day. By 60 days, you will own meaningful backend surfaces end to end. You will be shipping improvements across multiple systems and be responsible for how they behave under real customer workloads. By 90 days, you will be driving work without waiting for tightly scoped tickets: identifying what needs to be fixed or scaled, making the technical call, and shipping it. You will have materially improved how Moss performs, scales, or behaves in production. What We’re Looking For 5+ years building and operating production backend systems where latency, correctness, and reliability matter. A track record of hardening and scaling live, high-traffic systems without sacrificing quality. Strong distributed systems fundamentals across APIs, databases, caching, queues, and performance optimization. Hands-on experience with monitoring, alerting, incident response, capacity planning, and production SLAs. Experience working in compliant or regulated environments, ideally SOC 2, HIPAA, or similar. Strong instincts around data security, privacy, and operational rigor. Comfort operating across modern cloud infrastructure and making pragmatic architecture decisions. High ownership. You know what needs to be hardened first and do not wait for someone to hand you a checklist. Clear communication. You can work directly with customers, engineers, product, and GTM when something important is on the line. Nice to Have Experience building search, retrieval, vector, database, or other latency-sensitive infrastructure. Experience scaling systems by orders of magnitude or operating global, multi-region infrastructure. Experience taking a company through SOC 2 or HIPAA audits. Background in developer tools, infrastructure, API products, or AI platforms. Familiarity with edge compute, local-first systems, or on-device deployment. Familiarity with the modern AI stack and how developers build with LLMs. Why Moss This is a chance to own a core part of the product at a point where the technical decisions will shape how Moss scales for years. You will work closely with the founders, build systems that customers rely on every day, and have real input into the architecture, product, and engineering standards behind Moss. The work is technically hard: keeping retrieval fast, correct, and reliable as usage grows across different customers, workloads, and environments. Competitive compensation and meaningful equity.