Senior Python Backend Developer

We are looking for a Senior Python Developer to help scale a growing platform for smartwatches and tablets used by retail and hospitality businesses across Europe. The company provides devices and subscription-based infrastructure for a connected-device ecosystem. As the number of devices, customers and integrations grows, we need to strengthen the backend that supports reliable communication between devices and services. This is a deeply technical, hands-on role. You will build and improve backend services, solve connectivity issues and work closely with the Tech Lead and Android team. The team is working in hybrid model of work: 2-3 days from the office in Wrocław. Key responsibilities Build and develop backend features in Python.Improve the performance and reliability of services that support smartwatches, tablets and mobile communication.Investigate and fix connectivity issues, including delays, unstable device connections and TCP disconnects.Maintain and develop the communication layer between devices and backend services.Build and support integrations with external customer systems.Work with MQTT communication, including QoS settings, retained messages and broker configuration.Write clean, maintainable code and follow good engineering practices.Take part in code reviews and write automated tests to maintain strong code quality.Work closely with the Tech Lead and Android Developers on product and technical decisions.Help improve backend architecture as the platform, number of devices and customer integrations grow.Ideal candidate profile At least 4-5 years of commercial experience in backend development.Proven experience designing and building distributed systems, cloud-based applications or scalable backend services.Strong Python skills and hands-on experience with FastAPI, Django, Flask or a similar framework.Experience working with relational databases, especially MySQL, and non-relational databases, especially Redis.Good knowledge of MQTT, including QoS, retained messages and broker configuration with tools such as Mosquitto, HiveMQ or EMQX. MQTT configuration matters in connected-device systems because QoS defines message-delivery behaviour, while retained messages allow a broker to provide the most recent value for a topic to clients that subscribe laterSolid understanding of networking concepts, including TCP/IP, routing and load balancing.Experience with Docker and Git.Experience working in a cloud environment: AWS, GCP or Azure.Strong focus on clean code, automated testing, code quality and maintainable solutions.Technical university degree in Computer Science, Software Engineering or a related field.English at minimum B2 level, allowing comfortable day-to-day communication.Openness to hybrid work from the office (2-3 days per week) - it is important because the whole team is based in Wrocław.Conditions Work model: hybrid in Wrocław (2-3 days per week)Employment type: B2B or Contract of employment - it is up to you! You will be hired directly by customer, it is not outsourcing model.Salary: for B2B: 22 500 - 28 000 net/month, for Contract of employment: 18 000 - 23 000 PLN gross/monthBenefits: MultiSport card.Recruitment steps Phone call or online meeting with Recruiter from KUBO - 30 minutes.Technical interview - a 1.5-hour Microsoft Teams interview with the Tech Lead from the team.Final stage - a 1.5-hour in-person interview with the CEO in the office in Wrocław.Decision and feedback.