Job description
Description
At xfive, we are looking to expand our backend team with a mid- to senior-level engineer who brings expertise in Java and has a basic+ working knowledge of Python to help us deliver robust systems across a range of projects. In this full-time freelance role, you’ll do more than just code; you’ll communicate directly with clients and help shape the architecture of our solutions.
What We Offer
We’re all about building a team where you can thrive and do your best work. Here’s what you’ll love about working with us:
Freelance opportunity: Enjoy the flexibility of a freelance contract and earn between 25 and 35 USD per hour, depending on your experience and expertise.
Room to grow: We support continuous learning and professional development to help you advance your career.
Make an impact: Your ideas and work will directly influence our direction and help drive meaningful change.
Diverse projects: Work on exciting projects for startups, agencies, and companies based in the US, UK, and Australia.
Work your way: Choose to work from home, your favorite coffee shop, or our Kraków office (we’ve got a nice parking space too!).
Set your schedule: Work the hours that suit you best, as long as there’s some overlap with the team and clients.
Transparency: We’re open and honest about the company’s decisions, direction, and performance, so you’re always in the loop.
Supportive team: You’ll never be left alone. Our team is collaborative and always ready to help each other.
Great vibes: Join a team of open-minded, fun, and friendly people who enjoy what they do.
Stay connected: Participate in social events, both online and in person, to stay engaged and build connections.
Requirements
Must-Haves:
At least 6 years of professional software development experience, including:
5+ years with Java Spring Boot
2+ years with Python.
Strong verbal and written English communication skills (B2+ level), with the ability to talk directly with clients in online meetings.
Ability to deliver high-quality service and work independently.
Availability of at least 40 hours per week.
Solid programming fundamentals and understanding of best practices (e.g., DRY, KISS, abstraction, refactoring, optimization, security).
Strong understanding of software design patterns for scale and efficient code re-use.
Strong understanding of Microservices with OpenAPI, gRPC, and Protobufs.
Java:
Strong command of Java and Spring Boot.
Familiarity with non-relational databases like MongoDB.
Experience building RESTful APIs and working with microservices.
Understanding of Java concurrency and multi-threading.
Experience with testing frameworks like JUnit and Mockito.
Familiarity with Spring Security for authentication and authorization.
Proficiency with build tools such as Maven or Gradle.
Experience with containerization (Docker) and orchestration platforms (e.g., Kubernetes).
Good understanding of logging and monitoring tools for Java apps (e.g., SLF4J, Logback, ELK stack).
Familiarity with JVM performance tuning.
Python:
Solid grasp of Python 3.x syntax, idioms, and best practices.
Strong understanding of object-oriented and functional programming paradigms in Python.
Familiarity with virtual environments and dependency management tools (venv, pip, Poetry).
Proficiency in writing unit and integration tests with pytest or unittest.
Comfortable packaging modules and managing releases (e.g., setuptools, wheel, PyPI).
Experience with logging, debugging, and performance profiling (cProfile, logging module).
Basic knowledge of asynchronous programming with asyncio or async libraries
Ability to work with databases via ORMs or direct drivers.
Understanding of API serialization and request validation.
Nice-to-Haves:
Basic Polish proficiency (A2+level) to communicate with our local team.
Exposure to task queues and concurrency tools.
Familiarity with static typing and linting.
Experience containerizing Python applications.
Knowledge of CI/CD workflows for Python.
Hands-on with data-processing libraries (pandas, NumPy).
