Back End Developer

CyberproAI is looking for a highly experienced Senior Backend Engineer with strong, hands-on Python expertise to join our growing engineering team in Warsaw. This is a role for a senior engineer who loves solving complex technical challenges, designing scalable systems and building robust products that operate in real-world environments. You will work closely with engineering, product and AI teams to design and develop backend services, APIs and data-driven systems that are scalable, reliable and built to last. We are looking for someone who is not only an excellent Python developer, but also thinks architecturally, takes ownership and cares deeply about engineering quality. What You'll Do Design, build and maintain scalable backend applications and services using PythonDevelop robust REST APIs, microservices and backend integrationsOwn backend features from architecture and design through development, testing and productionWork on complex, data-intensive systems and high-volume backend workflowsCollaborate closely with Product, AI, Frontend, QA and DevOps teamsParticipate in architectural decisions and help shape technical directionImprove system performance, scalability, reliability and maintainabilityWrite clean, efficient and well-tested production codeConduct code reviews and contribute to engineering best practicesTroubleshoot and resolve complex production issuesMentor other developers and share technical knowledge across the teamContinuously evaluate new technologies and improve development practices What You'll Bring 5+ years of professional backend development experienceStrong and recent hands-on Python experienceExcellent understanding of backend architecture and software engineering principlesExperience developing production-grade APIs and microservicesStrong experience with FastAPI, Flask or DjangoExperience with relational databases such as PostgreSQLExperience with technologies such as MongoDB, Redis, Kafka or RabbitMQStrong understanding of distributed systems and asynchronous programmingExperience with DockerExperience working with AWS, Azure or GCPFamiliarity with Kubernetes and containerized production environmentsStrong understanding of CI/CD, automated testing and modern engineering workflowsStrong problem-solving and debugging abilitiesExcellent English communication skills What Will Make You Stand Out Experience working on AI, machine learning or data-intensive productsExperience integrating AI or LLM services into production backend systemsStrong experience with FastAPI and asynchronous PythonProven system design and architecture experienceExperience building systems operating at significant scaleStrong Kubernetes experienceExperience with event-driven or distributed architecturesPrevious experience in cybersecurity, SaaS or complex B2B technology productsOpen-source contributions or strong personal technical projectsExperience mentoring or technically leading other engineers The Person We're Looking For You are a senior engineer who still loves to code. You can take a complex problem, understand the bigger architectural picture and then get hands-on and build the solution. You care about quality, performance and clean design, but you also understand the importance of delivering. You are curious, independent and comfortable taking ownership. When something breaks, you investigate it. When something can be built better, you improve it. And when the team faces a difficult technical challenge, you are one of the people everyone wants in the room. If Python is your language, backend engineering is your craft and building complex products is what excites you, we would love to hear from you.