Mateusz Jedrzejewski

This was my masters dissertation for which I had spent a lot of time learning algorithms and methods of computer vision. Also read a few latest scientific articles on the matter. The final solution was implemented in C++ with OpenCV and utilized techniques such as optical flow and my own modification of a gaussian mixture model. It then proved to work on a few video samples I had acquired which gave me a lot of satisfaction.

This example application showcases my approach to domain-driven development programming. I've done this as a part of an interview for a company. It's a simple command-line application that asks the user about a book's name and then tries to look up the book's price on both Amazon and Apress. The most crucial aspect of the code is its division into domain, infrastructure, and application parts utilizing an inverted dependency model.

I was working on a backend for the video play out application written in REST microservice architecture using Java and Dropwizard.

It was extremely satisfying to see the applications that I implemented and overlooked from the first lines of code to finally go to production release and be continuously used by millions of customers.

The project was run in a very agile way (Scrum later Kanban), with strong TDD and constant pair programming.

I was deeply involved in the project and apart from taking part in planning of work, designing and implementing solutions, I introduced essential parts of the build process. Amongst other things, I worked on ansible configurations, package management, test execution on different environments or seamless deployment process implemented in Python.

Running production application was constantly monitored through both grafana and Kibana with the use of custom fine-tuned graphs and message logs to have maximum visibility of the running system, I was also one of initiators and main creators of a custom monitoring application written in angular.

The project involved on-demand support.

I was working as a contractor for UK tax office (HMRC) on the website to be used by all tax payers (individuals, companies and organizations) in the UK. It was written in microservice architecture with the use of Scala and Play framework and involved work on both front-end and back-end.

The project had really good automation process for creating new microservices so I did introduce a proper breakdown of business logic as per rules of REST and Domain Driven Design wherever I could. It also had a very efficient release process that used deployment pipeline and automated testing so I was often able to have my code in production in a few days.

It also had a strong Agile/Kanban process.

I worked in two crucial areas of the project - one being messages and alerts sent to the tax payers and another - the authorization system which was used by almost all other components.

I was constantly monitoring the running system and received alerts if anything wrong happened and the work involved finding and fixing issues on a live production system.

Overall it was a very satisfying project on which I have learnt a lot - from different details about how the deployment worked, to functional programming with asynchronous I/O.

It was a platform for slots and bingo games amongst others and had a user-base consisting of a few million people.

The main part of the backend was written as a large monolith Java application that exposed APIs to higher levels - the UI and games. The codebase did however follow some patterns of Domain Driven Design and the components were isolated from one another. It was a very interesting time as the company was expanding their business and new components were written as REST microservices with Java and Dropwizard. I worked on some very core and crucial parts positioned very low in the stack that involved manipulation of users funds. My work largely involved implementing new functionalities for existing components and also designing and implementing new components, cooperating directly with the architects and the product owners. I employed strong TDD and clean code principles. It also involved constant support and monitoring of a running production system including tracking down bugs and issues.

This work has been carried out for a different governmental department, was used by mainly Claimants and Job Agents to digitalize the processes needed for managing the benefit system in the whole of UK.

What was very interesting on this project was the domain, which was very complex. Implementing new features often required hands-on analysis of current manual practices that took place outside of the system, that also had a lot of vague and unclear parts to it, and then trying to design and implement then in the context of an already existing solution.

Also the codebase was common with a single repository so I have been working in various different areas.

The project was based on Java 8 and custom framework built on top of Dropwizard. Apart from implementing new features, I was involved in refactoring of existing legacy code, laying proposals of how it can be improved long-term. From time to time, I also fixed bugs and provided support of the running system.