Java Developer (with Python proficiency)

Job 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.

Job 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).

On-site, Remote, Hybrid

Krakow, Małopolskie, Poland

$25 - $35 per hour

Development