Senior Backend Engineer (Java, Kotlin, Spring Boot, AWS) (B2B)

🏢 Summary: Join a QA Backend Engineer role focused on ensuring the quality, stability, and reliability of complex distributed applications. You will test end-to-end backend processes, microservice integrations, and messaging flows while collaborating with development teams throughout the SDLC. The offer includes a hybrid work model, B2B cooperation, and benefits such as private healthcare, life insurance, Multisport, and e-learning access. 🗂️ Requirements: 5+ years of software testing experience, Backend testing experience, Microservices testing experience, Integration, system, usability, E2E and UAT testing, Test planning, analysis, execution and evaluation, Test design techniques, Asynchronous and event-driven systems, AWS SNS/SQS integration testing, SDLC knowledge, Defect management tools, Test management tools, API testing tools, SQL databases, Log analysis, request tracing and data-flow validation, Agile experience, Analytical and problem-solving skills, Communication and cross-team collaboration skills 📃 Skills: Testing, Microservices, AWS, SNS, SQS, SDLC, Jira, YouTrack, TestRail, Xray, Postman, Swagger, SQL, Agile, API, E2E, UAT 🏢 Description: Location : Hybrid work model (Warsaw, Mokotów). Onsite presence required on Thursdays and during PI Planning sessions Availability: ASAP / within 1 month Contract Type: B2B via Experis About the Role We are looking for a QA Backend Engineer to join a dynamic product development environment. In this role, you will be responsible for ensuring the quality, stability, and reliability of complex applications and integrations. You will work closely with multiple development teams, validating end-to-end business processes and backend flows across distributed systems and microservice-based architectures. Responsibilities Plan and execute integration, system, and usability testing activities Participate in End-to-End (E2E) and User Acceptance Testing (UAT) Validate complex backend processes across multiple microservices and integrations Analyze test results and identify potential risks affecting product quality and stability Work closely with developers to understand critical business and technical flows Analyze logs, trace requests, and validate data flow across services Support defect management and resolution activities Build strong cooperation with multiple development teams Collaborate with cross-functional and cross-team stakeholders to continuously improve product quality Contribute to testing strategy, planning, execution, and evaluation throughout the software development lifecycle Requirements At least 5 years of experience as a Software Tester Experience in planning, analyzing, executing, and evaluating tests Strong knowledge of common test design techniques Strong analytical and problem-solving skills Strong backend-focused testing experience Experience testing microservice-based architectures across multiple services Understanding of asynchronous and event-driven systems Experience with AWS SNS/SQS integrations and messaging flows Understanding of mobile and web-based applications Good understanding of the Software Development Lifecycle (SDLC) Experience with defect management tools such as Jira or YouTrack Experience with test management tools such as TestRail or Xray Experience using API testing tools such as Postman and Swagger Experience working with SQL databases Ability to analyze logs, trace requests, and validate data flows Experience working in Agile environments Strong communication and collaboration skills Ability to work effectively with multiple development teams Highly motivated team player with a proactive attitude Nice to Have Experience with test automation for mobile and web applications Knowledge of REST API standards, HTTP protocols, and API contract validation Experience within card payments or card management domains ISTQB Foundation Level and/or ISTQB Advanced Test Analyst certification Offer : Multisport card Private healthcare (Medicover) Access to an e learning platform Group life insurance

🏢 Summary: Join an early-stage product team to design and deliver scalable, high-volume backend systems using Node.js, TypeScript, and AWS. The role offers end-to-end ownership, influence over architecture and engineering practices, and mentoring responsibilities in a hybrid Kraków setup. 🗂️ Requirements: 5+ years of production software development with Node.js and TypeScript, Practical AWS knowledge, Distributed systems design knowledge, Scalability knowledge, Event-driven architecture experience, Automated testing experience, Independent problem-solving ability, English communication skills, Ability to work in an evolving, fast-paced environment 📃 Skills: Node.js, TypeScript, AWS, Lambda, ECS, S3, RDS, Jest, Vitest, Playwright 🏢 Description: Senior Backend Engineer: Node.js & AWS Location: Kraków, Poland Working model: Hybrid Contract: Employment agreement or B2B Build high-scale systems from the beginning We’re hiring an experienced backend engineer to join a growing international technology business as it expands its engineering presence in Kraków. This is an opportunity to help create a new product rather than inherit a finished roadmap. You’ll influence early technical decisions, build systems designed for demanding workloads, and take meaningful ownership from architecture through production. The company develops robust data infrastructure used by organizations operating in complex, high-stakes environments. Its technology processes large volumes of information and supports products where speed, availability, and accuracy genuinely matter. If you enjoy solving difficult engineering problems, making pragmatic architectural decisions, and seeing your work reach production, this role offers plenty of room to make an impact. What you’ll be doing Design and deliver scalable backend services with Node.js and TypeScript. Build APIs and asynchronous, event-driven workflows in AWS. Engineer reliable systems capable of supporting intensive, high-volume workloads. Own features throughout their lifecycle, from technical discovery and design to deployment and ongoing improvement. Help establish the architecture and engineering practices of a new product. Partner with product specialists and engineers across multiple disciplines. Support other developers through mentoring, thoughtful reviews, and knowledge sharing. Strengthen standards around testing, security, maintainability, and operational reliability. Respond constructively as requirements evolve and new technical challenges emerge. What we’re looking for At least five years of professional experience building production software with Node.js and TypeScript. Strong practical knowledge of AWS. Experience with services such as Lambda, ECS, S3, or RDS is especially relevant. A solid understanding of distributed system design, scalability, and event-driven architecture. Experience using modern automated testing tools such as Jest, Vitest, or Playwright. The confidence to investigate unfamiliar problems and move work forward independently. Clear English communication skills. Comfort working in an energetic environment where priorities and products continue to evolve. Additional experience we’d value You don’t need to bring everything on this list, but any of the following would be useful: Go development. Distributed platforms or messaging-based systems. Large language models or contemporary AI development tools. React. Relational and non-relational databases. Docker and Kubernetes. CI/CD pipelines and modern delivery practices. Why consider this opportunity? Join at an early stage and help shape a product’s technical direction. Work on challenging systems where performance and reliability are fundamental. Take genuine ownership without unnecessary layers of decision-making. Become part of a new engineering group in Kraków with room to influence how it develops. Collaborate in an international, English-speaking environment. Choose between an employment contract and a B2B arrangement. Work within a hybrid model in Kraków. Join a profitable, expanding business focused on sustainable long-term growth.