Leszek Ciesielski

Drove evolution of a .NET monolithic codebase towards a modern .NET Core based service oriented architecture running on Kubernetes (Amazon EKS). Introduced TDD, code reviews, automated code checks. Worked closely with the DevOps team on automated deployments, monitoring, performance management. Coached other team members.

Part of a five person team delivering and extending a system capable of processing up to 500GB of asset deliveries and sending out more than 2TB of music streams per day. Used RabbitMQ, MongoDB and .NET applications for the ingestion pipeline and GlusterFS as final storage. Some of my individual contributions included rewriting the build process to run on TeamCity instead of individual developer machines and guiding the team towards stricter adherence to Kanban and pair programming principles.

Worked as part of a Kanban-driven team, with a huge focus on TDD and pair programming. Main task was maintaining and improving an SOA-powered REST API, built with various ASP.NET frameworks and deployed across a cluster of servers. During that period the number of requests increased by 130%, to 240 per second. I also led the effort to enable compression across all services, which decreased the internal traffic volume by 30%.

Led a team developing .NET ETL software used by J.P. Morgan, M&G Investments and Schroders. Fixed performance issues and long standing bugs, including memory leaks and stability problems. Decreased the memory usage by 85% by rewriting performance-critical paths using no-copy .NET framework capabilities. Enhanced existing test harness by replacing unreliable tests and deployed new distributed continuous integration infrastructure based on Jenkins, which reduced build times by half. Mentored team members.

Worked as part of a team that delivered intra- and extranet portals for large London clients using Scrum project flow. Leveraged Microsoft ASP.NET MVC, Microsoft Sql Server and Sitecore for complete CMS solutions. Used load testing, profiling and live site metrics to decrease response times, page size and website cost of operation with caching (both in-app and at HTTP level), output compression, asset optimisation and CDN re-configuration.

Developing cash register / storehouse management systems for retail chains. Developing Linux-targeted applications, using managed (C#) code. Contributing to Mono project. Managing build/testing automation for internal projects.