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Konstanty Orzeszko

Verified Expert in Engineering

Full-stack Developer

Warsaw, Poland

Toptal member since December 11, 2021

Expertise

Back-end Developers Full-stack LLM Front End REST API C#.NET WPF Jira Xamarin Android iOS Flutter Python

Bio

Konstanty is a seasoned software engineer with experience spanning across various back-end and mobile environments. As an expert in software development and architecture, he understands that clean code and a good foundation are essential. With his systems administration knowledge and console scripting, he created CI/CD pipelines for many projects. Konstanty uses behavior-driven development and domain-driven design to significantly improve stakeholders' satisfaction with the developed product.

Portfolio

PricewaterhouseCoopers (PwC)

.NET 8, Azure Functions, Azure Durable Functions, Azure AI Search...

Polish Security Printing Works

ASP.NET MVC, Behavior-driven Development (BDD), Test-driven Development (TDD)...

PLATONIC Tech UG

Flutter, C#.NET, Mobile, Mobile Apps, APIs, REST, Firebase, Firebase iOS SDK...

Experience

APIs - 9 years
C# - 9 years
REST - 8 years
DevOps - 6 years
Microservices - 5 years
ASP.NET MVC - 4 years
Python - 2 years
Behavior-driven Development (BDD) - 2 years

Preferred Environment

ASP.NET MVC, Behavior-driven Development (BDD), DevOps, SQL, Python, Flutter, Architecture

The most amazing...

...thing I've developed is the eDO App, ranked #7 as the productivity app in the App Store that utilizes NFC to read data from the Polish ID.

Work Experience

Lead Software Engineer

2024 - PRESENT

PricewaterhouseCoopers (PwC)

Led and supervised the back-end development team working in a microservices architecture based on .NET 8 and Azure.
Built ETL/ELT processes leveraging Azure Functions, Durable Functions, and Event Grid.
Defined and implemented Master Data architecture, ensuring consistency and referential integrity across the platform.
Developed core back-end components for financial computation, large-scale data processing, and inter-service communication.
Integrated Azure AI Search and Cosmos DB for fast, intelligent data retrieval and analytics.
Oversaw CI/CD processes, quality standards, and architectural governance in Azure DevOps.
Collaborated closely with Data Engineering and AI teams to design optimized data pipelines.
Delivered a cloud-native, data-driven EPR platform automating compliance reporting and financial calculations for multinational clients.

Technologies: .NET 8, Azure Functions, Azure Durable Functions, Azure AI Search, Azure Cosmos DB, Databricks, Azure Databricks, Azure Data Lake, Azure Storage, Azure DevOps, Microservices, Serverless, Architecture, Python, DevOps, ETL, ELT, ASP.NET, Azure Cloud Services, SQL Server 7, Back-end Development, FastAPI, Asynchronous Programming, Large Language Models (LLMs), Pandas, Pytest, REST APIs, Performance Optimization

Lead ASP.NET Developer

2020 - 2024

Polish Security Printing Works

Developed the OAuth 2.0-based back,end for identity management and personal data sharing.
Facilitated the online event stormings via Miro. Documented results and supervised development.
Designed and supervised the usage of strict project architecture.
Collaborated with the DevOps team on Kubernetes deployment on the on-premise cloud.
Created multiple test suites to mimic partner integrations with Azure Web Apps, Azure Static Web Apps with Blazor WebAssembly (Wasm), and Azure Functions with C#.

Technologies: ASP.NET MVC, Behavior-driven Development (BDD), Test-driven Development (TDD), Domain-driven Design (DDD), Kubernetes, Docker, PostgreSQL, Marten, Azure Functions, Azure Websites, Blazor, Technical Hiring, Code Review, Source Code Review, Interviewing, Task Analysis, Back-end, ASP.NET Core, Azure, Full-stack, Front-end, Google Cloud Platform (GCP), Architecture, Leadership, Desktop Web Design, C#.NET, ASP.NET, SQL Server 7, Back-end Development, Asynchronous Programming, Large Language Models (LLMs), Pytest, REST APIs

Full-stack Flutter and .NET Developer

2023 - 2023

PLATONIC Tech UG

Fixed bugs from previous versions of the application.
Revamped the mobile UI entirely based on Figma prototypes.
Automated the CI/CD of the Azure back end and both Android and iOS applications.
Reduced server response times in critical places by a factor of 20.

Technologies: Flutter, C#.NET, Mobile, Mobile Apps, APIs, REST, Firebase, Firebase iOS SDK, Firebase Analytics, Cloud Firestore, Fastlane, Facebook SDK, Google Sign-in, Single Sign-on (SSO), Azure Table Storage, Azure Websites, Azure SQL, Azure Blob Storage API, Android, iOS, MVC Design, Azure Cloud Services, SQL Server 7, Minimum Viable Product (MVP), Cross-platform App Development, Back-end Development, FastAPI, REST APIs, Performance Optimization

Flutter Developer

2022 - 2023

Jacob Levitt

Developed new functionalities based on saving application states between loads.
Moved the back end from a slow WordPress solution to a blazingly fast CDN server. Optimized the costs of serving high-quality photos.
Helped in the process of transferring ownership on both the Play Store and App Store. Also launched new versions of the apps.

Technologies: Flutter, Dart, Full-stack, Mobile, Mobile Apps, Android, iOS, APIs, Minimum Viable Product (MVP), Cross-platform App Development, Asynchronous Programming, REST APIs

Developer Screener

2022 - 2022

Toptal

Achieved a higher than usual satisfactory rate of interviewed rejected developers, thanks to my soft skills.
Trained new screeners by either letting them shadow my calls or by coworking background checks on candidates.
Engaged in recruitment processes of over 230 candidates, performing code reviews and checking architectural knowledge and soft skills.

Technologies: JavaScript, C#, React, Dart, Flutter, Windows Desktop, FastAPI, Pytest, REST APIs

Xamarin Team Leader

2017 - 2020

Polish Security Printing Works

Created, led, and managed a team of three Xamarin developers, one back-end developer, two testers, and one analyst. I delivered every project on time.
Followed the Scrum methodology, facilitated planning, presented every increment during sprint reviews, and handled stakeholder interactions.
Implemented the screens and flows designed by GFX and UX teams via Adobe XD.
Created and maintained the CI/CD pipeline, including running unit tests on mobiles, local automated UI testing, UI testing on AppCenter cloud farm, and deployment on multiple testing groups and respective stores.

Technologies: ASP.NET MVC, Xamarin.Forms, Xamarin.iOS, Xamarin.Android, Adobe Experience Design (XD), Blockchain, PostgreSQL, Scrum, Visual Studio App Center, DevOps, GitLab CI/CD, Observer Pattern, Code Review, Task Analysis, Technical Hiring, Interviewing, Source Code Review, Android, iOS, Mobile Apps, Firebase, Cloud Firestore, Leadership, Requirements Analysis, Software Design, Architecture, C#.NET, ASP.NET, Azure Cloud Services, SQL Server 7, Minimum Viable Product (MVP), Cross-platform App Development, Asynchronous Programming, REST APIs

.NET Developer

2015 - 2017

Polish Security Printing Works (PWPW)

Participated in developing the ERP system designed to handle the Polish ID production cycle comprehensively. The modules included ID ordering, document engraving, CR and QA, document shipping, and logistics.
Used Jira as a task management system for developing new functionalities and bug fixing.
Developed the custom-tailored CI/CD pipelines for a complex system deployed at restricted access areas without internet connectivity.

Technologies: Windows Presentation Foundation (WPF), DevExpress Controls, Oracle SQL, C#, Waterfall Methodology, Jira, XAML, Model View ViewModel (MVVM), Observer Pattern, Microsoft SQL Server, Desktop App Development, Desktop, C#.NET, ASP.NET, SQL Server 7, Back-end Development

Experience

eDO App

https://apps.apple.com/pl/app/edo-app/id1503023855?l=pl

The eDO app is an application that allows users to confirm their identity and create an electronic signature securely. It is a Xamarin native mobile application for iOS and Android, providing the requesting parties with personal information stored on a Polish passport and ID. The application utilizes NFC to access data, while back-end services provide data to the connected partners via OAuth 2.0.

I was the lead back-end developer and participated in the architecture and design of mobile applications.

Mobile Big Family Card

https://www.gov.pl/web/mobywatel/karta-duzej-rodziny-mkdr

I was the team leader for the first government-accepted digital document in Poland. The application provided users with access to proof of enrollment in the government benefits program and the ability to navigate to the nearest partners of the program. The app is written in Xamarin Forms for Android and iOS.

Polish ID Personalization System (SPD)

A .NET ERP system designed to comprehensively handle the Polish ID production cycle. Modules included ID ordering, document engraving, document CR and QA, and document shipping and logistics. The project took two years to complete. I began as a regular developer and finished as a senior overseeing both web API back end and front end in WPF.

Kontroler | Flutter App with IoC Communication

The Flutter app communicated with temperature and humidity sensors located at the production site via the BLE protocol.

The application's main objective was to monitor crucial parts of the factory line, which are hard and time-consuming to do by hand.

KASA | Desktop Application Communicating with Credit Card Terminals

A C# WPF front-end application communicating over REST framework with ASP.NET Web API. The server is managed and proxied TCP communication with multiple card terminals over clients' networks via SignalR.

The solution was installed over numerous government offices, allowing them to accept card payments.

Educational App for Medical Professionals

A Flutter-based app designed to help medical professionals identify dermatology issues. I was hired as a developer to fix a few issues and implement state persistence. During the engagement, I identified a bottleneck in the form of a slow back end and reimplemented it on a fast CDN and local caching.

Social App for Events

A Flutter app with a .NET back end hosted on Azure. I was the only developer hired to help with the application release. Initially, I fixed a few bugs, then revamped the entire front end based on Figma prototypes. Lastly, I implemented SSO (Google, Apple, and Meta) and increased the speed of most critical endpoints.

eDO Post (Secure e-Delivery System)

eDO Post is an enterprise-grade secure e-delivery platform developed for PWPW S.A. It enables encrypted, regulation-compliant document exchange between public administration, businesses, and citizens — equivalent to registered mail in a fully digital environment.

Election Oversight Platform

https://www.gov.pl/web/cyfryzacja/aplikacja-mezowie-zaufania

The “Mąż Zaufania” (Trusted Representative) application was designed to support legal requirements for reporting irregularities during national elections. The system allowed registered users to submit verified reports, including text and media attachments, from polling stations across the country. Handling huge spikes of users during elections

Education

2012 - 2016

Engineer's Degree in Computer Science

Polish-Japanese Academy of Information Technology - Warsaw, Poland

Skills

Libraries/APIs

Pandas, REST APIs, Xamarin.iOS, Xamarin.Android, React, Web API, Firebase iOS SDK, Facebook SDK, Azure Blob Storage API

Tools

Jira, Visual Studio App Center, Adobe Experience Design (XD), GitLab CI/CD, Pytest, Firebase Analytics, Fastlane, Sqitch

Languages

C#, XAML, Python, C#.NET, Dart, SQL, JavaScript

Frameworks

Windows Presentation Foundation (WPF), Entity Framework Core, ASP.NET MVC, .NET Core, .NET, ASP.NET Core, Flutter, ASP.NET, Blazor, iOS SDK, Android SDK, .NET 8

Paradigms

Model View ViewModel (MVVM), Mobile Development, Requirements Analysis, Desktop Web Design, Desktop App Development, REST, Asynchronous Programming, Behavior-driven Development (BDD), DevOps, Scrum, Test-driven Development (TDD), MVC Design, Azure DevOps, Microservices, ETL

Platforms

Xamarin, Android, iOS, Desktop, Windows Phone 8, Docker, Azure, Bluetooth Low Energy (LE), Firebase, Blockchain, Kubernetes, Azure Functions, Google Cloud Platform (GCP), Windows Desktop, Mobile, Azure AI Search, Databricks

Storage

PostgreSQL, Microsoft SQL Server, Cloud Firestore, Azure Cloud Services, SQL Server 7, Redis, Oracle SQL, Azure Websites, Azure Table Storage, Azure SQL, Azure Cosmos DB, Azure Storage, Google Cloud Storage

Other

DevExpress Controls, Xamarin.Forms, Code Review, Task Analysis, Technical Hiring, Interviewing, Source Code Review, Back-end, Mobile Apps, Front-end, Full-stack, Full-stack Development, Leadership, Software Design, Architecture, Minimum Viable Product (MVP), Cross-platform App Development, Event-driven Systems, Back-end Development, FastAPI, Large Language Models (LLMs), Industrial Internet of Things (IIoT), Internet of Things (IoT), Performance Optimization, Domain-driven Design (DDD), Waterfall Methodology, Marten, Observer Pattern, Akka.NET, Web Development, DevExpress, TCP/IP, APIs, Google Sign-in, Single Sign-on (SSO), Azure Durable Functions, Azure Databricks, Azure Data Lake, Serverless, ELT, Pub/Sub, GitOps, Argo CD, Google Cloud Functions

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