
Bjorn Stiel
Verified Expert in Engineering
Software Developer
Bjorn is a senior Python developer who spent over a decade building robust and scalable applications for clients such as Credit Suisse. He specializes in distributed workflows via Celery and REST APIs using Django, Flask, and Falcon. He developed an app for UBS Investment Bank that helped their trading desks manage multi-billion dollar risk. Bjorn's expertise with complex integrations prove invaluable in projects where precision matters most.
Portfolio
Experience
Availability
Preferred Environment
Windows, Linux, Docker, Visual Studio Code (VS Code)
The most amazing...
...app I've developed makes Excel workbook files work seamlessly with Git.
Work Experience
Technical Co-founder
xltrail
- Developed a web app on top of Git that facilitates version control and collaboration for Excel.
- Built the first iteration and brought it to market. The app is used by on-premise and Cloud customers, primarily in the financial services industry. The app supports various deployment targets: Cloud, on-premise, and airgapped on-premise and integrates with enterprise LDAP/AD systems for user (and licensed seats) management.
Python Developer
Freelance Financial Technology Consulting
- Developed bespoke Python-based solutions to a number of clients in the financial services industry (hedge funds, asset managers, trading desks), primarily in London and Zurich.
- Built Celery-based apps for scheduling complex asynchronous workflows-long-running calculations as well as highly concurrent data flows to and from third-party systems (Bloomberg). Leveraged Django, Flask, SQLALchemy, and Falcon to deliver REST APIs.
- Delivered containerized apps for easy CI/CD and deployment, leveraging GitLab pipelines.
- Integrated legacy Excel/VBA applications with client-side Python code (via xlwings), server-side REST APIs and Bloomberg (via BLPAPI and Data License).
- Integrated Django/Flask REST apps with customer's LDAP/Active Directory infrastructure for authentication and authorisation.
- Helped customers integrate and replace Excel with Jupyter notebooks.
Rapid Application Development Consultant
Credit Suisse
- Developed a number of tactical Python solutions for the equity trading desks in London.
- Integrated legacy Excel applications with modern REST APIs.
- Spearheaded a data science project to extract historical quantitative data from non-structured data using Pandas.
- Built various rapid application Excel/VBA applications.
Quant and Rapid Application Developer
UBS Investment Bank
- Developed a new platform for the bank's commodity index business that enabled them to better risk-manage their complex trading book.
- Built a Python-based backtesting platform that enabled users to rapidly prototype and launch new alpha- and beta trading strategies.
- Oversaw and managed new product launches resulting in additional revenues to the business.
- Introduced Excel-DNA to rapidly build Excel Add-Ins in C#, facilitating a modern integration between Excel and internal REST APIs and Bloomberg's BLPAPI.
Junior Risk Controller
Landesbank Berlin
- Developed a suite of C++ and Excel-based tools improving the bank's ability to monitor the risk of its equity derivative portfolio.
- Integrated internal (Murex) and external data feeds (Bloomberg) into the risk system.
- Streamlined the department's internal RFC process to ensure a faster and higher quality release process.
Experience
Version Control and Collaboration App for Excel
http://www.xltrail.comxlwings | Python for Excel
https://www.xlwings.org/Trading and Execution System
Skills
Languages
Python, Falcon, Excel VBA, Visual Basic, Visual Basic for Applications (VBA), SQL, C#
Frameworks
Flask, Django, Django REST Framework
Libraries/APIs
SQLAlchemy, Bloomberg API, Interactive Brokers API, Pandas
Tools
Celery, Git, Microsoft Excel, Excel-DNA, Docker Compose, Visual Studio Tools for Office (VSTO), Pytest
Platforms
Docker, Jupyter Notebook, Visual Studio Code (VS Code), Linux, Windows, Kubernetes
Other
xlwings, Trading, Trading Applications, APIs, API Integration, Web Scraping, Finance, Data Processing, Integration, Investments, Investment Manager, Back-end, Data Analysis, Options Trading, Algorithmic Trading, Backtesting Trading Strategies, Algorithms, LDAP
Storage
PostgreSQL
Education
Master's Degree in Financial Engineering
Birkbeck College, University of London - London, United Kingdom
Master's Degree in Business Economics
Free University of Berlin - Berlin, Germany