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Radosław Szalski, Python Developer in Poznań, Poland
Radosław Szalski

Python Developer in Poznań, Poland

Member since February 4, 2017
Radosław is a Python enthusiast, self-starter, and full-stack web developer. He has over six years of professional experience engineering web applications. While working with many different technologies, he focuses on full-stack development, craftsmanship, and testing processes. He enjoys automating things with Ansible/Terraform and learning new technologies, and he is experienced with recruiting and onboarding engineers.
Radosław is now available for hire


  • LudosProject
    Python, React, React Native, AWS, Ansible, Terraform, Packer, Prometheus...
  • Croscon (via Toptal)
    Python, Flask, React, Backbone, Marionette, Docker, Celery, SQLAlchemy...
  • STX Next
    Python, JavaScript, jQuery, Ansible, Vagrant, Supervisord, Git, Pyramid...


  • Python, 6 years
  • JavaScript, 4 years
  • Docker, 3 years
  • Ansible, 3 years
  • Terraform, 2 years
  • Amazon Web Services (AWS), 2 years
  • React, 1 year
  • React Native, 1 year
Poznań, Poland



Preferred Environment

MacOS/Linux, Git, PyCharm, Zsh, Chrome dev tools

The most amazing...

...project I've developed is an intuitive library to recursively parse XML documents into interactive Python objects and back.


  • CTO
    2016 - PRESENT
    • Screened, recruited, and coached Python, JavaScript, and Unity developers.
    • Performed extensive code reviews.
    • Orchestrated dozens of virtual servers and databases, across multiple environments on AWS using Ansible, Terraform, and Packer.
    • Owned all architectural choices.
    • Created production-quality REST APIs in Python with authentication, logging, and metrics instrumentation (using Prometheus).
    • Performed load testing and benchmarking of every developed microservice using, Ab, Apib, and Wrk.
    • Designed, implemented, and maintained back-ends on Amazon Web Services for various games and applications.
    • Designed gorgeous metric dashboards using Grafana that allow every team member to see a high-level overview of the environments as well as dig into details if needed. Data sources included: AWS CloudWatch metrics, self-hosted Prometheus instance, and SQL connectors.
    • Benchmarked and tuned the whole application stack from Linux kernel parameters through Nginx/uWSGI configuration options to AWS design choices.
    • Consulted as the go-to guy for hard technical and business problems for the whole team.
    • Negotiated with clients and analyzed requirements for upcoming games and services.
    Technologies: Python, React, React Native, AWS, Ansible, Terraform, Packer, Prometheus, Grafana, Flask, Falcon, SQLAlchemy, Alembic, Django, GitHub, AWS Lambda,
  • Senior Python Developer
    2018 - 2018
    Croscon (via Toptal)
    • Extended and fixed business-critical functionality for live customers.
    • Worked on asynchronous file import/export endpoints for high-volume bulk transfers.
    • Implemented new end-user workflows involving schema migrations.
    • Integrated a React web app with REST API.
    • Improved code coverage by writing functional and unit tests for new and existing code.
    • Introduced type hints to a Python 3.6-based project.
    • Migrated Peewee ORM from version 2.x to 3.x in an API with complex queries.
    • Worked with MySQL with custom DB-level encryption requiring key sharing through Celery tasks.
    Technologies: Python, Flask, React, Backbone, Marionette, Docker, Celery, SQLAlchemy, Peewee, MySQL
  • Senior Full-stack/Python Engineer, Team Lead
    2015 - 2017
    STX Next
    • Managed multiple products in the whole project.
    • Decided on architecture for each application.
    • Analyzed client requirements and advised clients on technology choices.
    • Managed the whole software development cycle of multiple, cross-dependent production services.
    • Developed a branching strategy in Mercurial.
    • Reviewed code for every change made by every developer in my team.
    • Advocated and coached team members on pair programming and automated testing.
    • Owned and handled DevOps tasks, including orchestration and configuration management of environments and services using Ansible and Vagrant.
    • Ensured that complicated and intertwined stuff worked according to business rules.
    • Maintained multiple production applications, both legacy and greenfield.
    • Wrote documentation and tutorials for new developers.
    • Gave technical interviews and provided technical onboarding for many highly skilled employees.
    • Profiled and optimized performance of back-end Python code and front-end JavaScript.
    • Managed the whole team: trained and coached them, performed appraisals, and planned goals for upcoming months.
    Technologies: Python, JavaScript, jQuery, Ansible, Vagrant, Supervisord, Git, Pyramid, Mercurial, rST, SVN, CVS, JIRA
  • Senior Python Engineer
    2014 - 2015
    STX Next
    • Worked in Agile teams on multiple production services for the banking sector delivering immense business value.
    • Analyzed complicated requirements and planned work for Scrum sprints.
    • Managed and improved a legacy codebase while simultaneously delivering business value by developing new features.
    • Presented products to new and existing clients.
    • Advised clients on technology choices.
    • Managed a Jenkins CI server, BI dashboards, and multiple virtual servers.
    • Focused on quality, automating unit and integration tests.
    • Educated colleagues on proper testing, mocking techniques, and advanced VCS usage.
    • Continuously improved code testability and maintainability even in the legacy parts of the system.
    Technologies: Python, JavaScript, jQuery, Ansible, Pyramid, PyTest, Git, Mercurial, Jenkins, Fabric
  • Technical Referent
    2013 - 2014
    Poznan University of Technology
    • Ensured that researchers and students had working equipment and environments to work with.
    • Managed computer networks, CS lab equipment, and various on-premises hosted platforms (ticketing system, project management software).
    • Automated the provisioning of OSes in every lab using TFTP and PXE.
    Technologies: Python, TFTP, PXE, Linux
  • Software Engineer/Researcher
    2012 - 2014
    Poznan University of Technology
    • Developed a network testbed management framework in Python for scheduling experiments on wireless nodes.
    • Designed an experiment description language and parser allowing reproducible test runs on this framework.
    • Developed Linux kernel modules integrating with a Linux network stack and improving QoS scheduling.
    • Designed and implemented crawlers/scrapers for Twitter and Facebook (both API and front-pages) using Java.
    • Developed SIP clients integrating with a self-hosted Open IP multimedia subsystem.
    • Wrote academic papers and performed wireless network related research.
    • Designed experiment scenarios and user stories to be included in my papers.
    • Supervised work of students and interns.
    Technologies: Python, Fabric, Invoke, Java, C, SIP, OpenIMS, LaTeX, UML


  • Coinego – React Native Cryptocurrency Portfolio Manager (Development)

    • Developed from scratch
    • Observe selected coin prices, get notified on changes
    • Define your crypto portfolio to see its worth
    • Integration with REST API for coin prices
    • Fully automated CI/CD pipeline with Bitrise and Fastlane, automatic deploys to Play Store
    • Redux, Saga, Flow, Jest, Standard

  • React Native Demo Project (Development)

    A To Do list manager written using React Native.

    • Front-end created in React Native for iOS/Android enabling the management of tasks with support for attachments
    • Access to Camera API (taking photos, media library)
    * Access to Contacts API
    • Access to Share API
    • State management with Redux and Redux-Saga
    • Back-end REST API created in Python using Django + Django REST Framework
    • JWT token authentication
    • Automated tests with Jest/Enzyme/PyTest
    • Linting: eslint/pylint

  • Idle Car Factory | Mobile Game Back-end (Development)

    Created the back-end architecture for a mobile game that has over 500,000 installs and receives hundreds of requests per second on Amazon Web Services. The architecture consists of a tier of web servers hosting a REST API written in Python (by me), load balancers, and PostgreSQL database. All of this managed using infrastructure as code where every resource is represented in Terraform and all of the servers are provisoned using Ansible. This allows for rapid deployment of multiple copies of whole environments and ensures that every change is versioned and documented.

  • Python SDK for the YOTI Platform (via Immergo) (Development)

    Designed and implemented a Python SDK for the YOTI platform. Designed plugins for Flask and Django that used this SDK. Coordinated work of other Python programmers. Communicated with both business and programmers.

  • Mappet | XML To/From Python Mapper (Development)

    This is a pure Python library developed to ease the pain of working with XML-based APIs and ESBs. It includes an elegant XML recursive parser based on lxml, which allows every XML document to be represented as a Python object. Such an object allows one to access XML nodes/attrs/children as object attributes, which makes it very intuitive to use. This library has a very high unit test coverage and has been open sourced thanks to my efforts while working in STX Next.

  • eRFC | RFC to Ebook Converter (Development)

    This is a simple Python project exhibiting the Unix tool philosophy, "Do one thing well." It is the result of my frustration with the formatting of plain-text RFCs on Kindle. It is well documented and has a simple and elegant CLI interface (created with docopt library).

  • | PSU Reviews Crawler (Development)

    This is a Python crawler for power supply unit reviews on the fantastic and thorough website. Written using the most popular crawling library in Python, Scrapy, it illustrates my approach to challenges: Automate it and share with the world.

    Because having a good PSU for your PC is really important.

  • Terraform AWS Cloud: Sane Infrastructure Management (Publication)
    Writing an application is only part of the story. In order for it to be of value, it needs deploying somewhere it can scale; it has to run with high availability, have backups, and so on. Deployment and infrastructure management isn’t a simple process. And Terraform does nothing to hide the complexity. However, it does make your infrastructure declarative and reproducible, like your code. In this article, Toptal Freelance DevOps Engineer Radosław Szalski teaches us what Terraform is, how its components work, and how to configure an entire AWS Cloud solution in minutes using its configuration language.


  • Languages

    Python, Python 3, JavaScript, Falcon, HTML, HTML5, SQL, CSS, Bash, CSS3, Sass
  • Libraries/APIs

    REST API, jQuery, Flask-RESTful, React, React Redux, react-navigation, Redux-saga, Asyncio
  • Tools

    PyCharm, Mercurial, Vagrant, Pytest, Docker Compose, PDB, Nginx, Git, Ansible, Packer, Terraform, VirtualBox, Grafana, Travis CI, AWS ECS, AWS CodeBuild, LaTeX, Sublime Text, Jenkins
  • Paradigms

    Unit Testing, REST, Agile Software Development, Functional Programming, Microservices Architecture, Extreme programming, Scrum, Kanban, Test-driven Development (TDD), Object-oriented Programming (OOP), DRY, KISS
  • Platforms

    Docker, Bitrise, Amazon Web Services (AWS), Visual Studio Code, Linux, Linode, Android
  • Other

    GitFlow, Full-stack, Code Review, Architecture, Prometheus, Google Play Store, App Store, AWS CodePipeline, AWS Route 53, Mentorship, Google Material Design
  • Frameworks

    Flask, Pyramid, Django REST Framework, React Native, Redux, Django
  • Storage

    PostgreSQL, MySQL, AWS S3, AWS RDS, Redis, SQLite


  • Master of Science degree in Computer Science
    2014 - 2016
    Poznan University of Technology - Poznań, Poland
  • Bachelor of Science degree in Computer Science
    2010 - 2014
    Poznan University of Technology - Poznań, Poland
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