Bartosz is available for hire
Hire BartoszBartosz Frąckowiak
Verified Expert in Engineering
Software Engineer and Developer
Warsaw, Poland
Toptal member since April 7, 2022
Bio
Bartosz is a software architect with 16 years of experience in distributed systems. He owns the architecture of a SaaS platform spanning 20+ bounded contexts and drove its move from a .NET monolith to event-driven Azure services. Since 2025, he has co-led an AI transformation for several hundred engineers: agentic PR review, an MCP server for internal APIs, and Claude Code adoption. He did doctoral research on software architecture at the University of Warsaw.
Portfolio
EcoVadis
Management, .NET, Architecture, Design, Microservices Architecture...
Exemplar Human Services, LLC
Technical Leadership, .NET, Agile, Architecture, Database Architecture, ASP.NET...
Onward Travel Solutions Ltd
Laravel, Event-driven Architecture, Microservices, API Architecture...
Experience
- .NET - 14 years
- Software Architecture - 11 years
- Architecture - 11 years
- Software Design - 8 years
- Object-oriented Programming (OOP) - 8 years
- Distributed Systems - 6 years
- Distributed Architecture - 5 years
- Management - 4 years
Work Experience
Software Architect | Senior Staff Engineer
2022 - PRESENT
EcoVadis
- Owned the architecture of a supplier sustainability platform across 20+ bounded contexts and the enterprise API surface used by thousands of customers, partnering with product and engineering leaders to set direction.
- Co-led an organization-wide AI transformation for several hundred engineers, covering an agentic tech radar, Claude Code adoption, and prompt-driven architecture practices.
- Built an internal MCP server exposing core business APIs to AI agents, plus AI workflows for task analysis, pull request review, Sonar remediation, and living documentation kept in sync with code.
- Drove the shift from a legacy .NET monolith to event-driven Azure services using DDD, CQRS, an outbox pattern over Service Bus, and anti-corruption facades for dual-write bridging in the enterprise API migration.
- Authored reference patterns, led architecture reviews, and mentored staff and principal engineers, favoring evolutionary architecture over rewrites and ensuring coherent systems and well-balanced trade-offs across a strong engineering organization.
Technologies: Management, .NET, Architecture, Design, Microservices Architecture, Service-oriented Architecture (SOA), Microservices, Azure, Kubernetes, C#.NET, Microsoft SQL Server, HTML, ASP.NET, C#, LINQ, Enterprise Architecture, Platforms, Scalability, Containers, Analytics, Test Automation, Team Management, XML, Serverless Architecture, Elasticsearch, REST APIs, Databases, Event-driven Programming, Scaling, Back-end, SQL, Technical Leadership, Web Application Architecture, .NET Core, REST, Test-driven Development (TDD), Azure DevOps, ASP.NET Core, Back-end Architecture, Back-end Development, Microsoft Azure, HTTP REST, Entity Framework Core, Software Architecture, Leadership, Third-party APIs, Cloud Architecture, Azure SQL, Application Architecture, System Architecture, OpenAPI, REST API Architecture, System Architecture Design, Technical Documentation, Diagrams, Event-driven Architecture, Distributed Architecture, Endpoint Security, Entity Framework, Team Leadership, GitFlow, Project Management, Agile Project Management, NoSQL, Database Design, API Integration, Real-time Data, Windows PowerShell, Microsoft Graph API, Transact-SQL (T-SQL), JSON Web Tokens (JWT), Web App Development, Minimum Viable Product (MVP), API Architecture, Node.js, Back-office System Development, Web Architecture, DevOps, Continuous Integration (CI), Solution Architecture, OpenAI API, Creative Problem Solving, CI/CD Pipelines, Data Analysis, Microsoft Visual Studio, System Design, Integration, IIS, Windows Services, Legacy Software, DB, GraphQL, Enterprise Software, Software Project Management, Agile, Agile Software Development, Data Structures, Database Architecture, Agentic AI, Claude Code, Model Context Protocol (MCP), Large Language Models (LLMs), Domain-driven Design (DDD), CQRS, Azure Service Bus, Generative Artificial Intelligence (GenAI), AI Agents
[Toptal Teams] Tech Lead
2023 - 2023
Exemplar Human Services, LLC
- Conducted a code review of the current MVP, taking into consideration the architecture vision, the context of the application, security, and available resources.
- Defined the technical approach (technical flows, tech architecture, and recommended tech stack).
- Provided solutions architecture (the ability to prove the technology).
- Designed, built, and configured applications to meet business processes and application requirements.
- Defined architecture vision and evolution approach to achieve the goal, considering lose coupling, testability, maintainability, and time-to-market needs in the project context.
- Defined the CI/CD process and evolution for scaling pipelines with the size of the teams.
Technologies: Technical Leadership, .NET, Agile, Architecture, Database Architecture, ASP.NET, APIs, C#, Azure, Data Architecture, Data Structures, CI/CD Pipelines
Laravel Expert | Microservices Migration
2022 - 2022
Onward Travel Solutions Ltd
- Reviewed a microservice architecture, consulting existing solutions in the monolith architecture and defining the migration strategy.
- Defined the migration vision from monolith to micro-service.
- Delivered a vision document treating technical concepts proven to work in a microservices architecture.
Technologies: Laravel, Event-driven Architecture, Microservices, API Architecture, Software Architecture, APIs, Travel, RESTful Microservices, Microservices Architecture, Architecture, Web Architecture, Solution Architecture, OpenAI API, Creative Problem Solving, CI/CD Pipelines, System Design, Integration, PHP, IIS, DB, GraphQL, Enterprise Software, Software Project Management, Agile Software Development, Data Structures, Database Architecture
Technical Leader | Staff Engineer
2017 - 2022
EcoVadis
- Introduced CI/CD processes, domain-driven design methodology with event-driven architecture, and data-driven decision-making processes.
- Designed the applications' architecture, prototyped solutions, and developed back-end services.
- Cooperated with solution architects and technical leaders and established a software craftsmanship culture.
- Implemented and spread an open-source initiative at the organization.
- Migrated a legacy monolith application to a microservice architecture, scaling out 15-year legacy projects.
- Oversaw the technical development of several team members.
Technologies: .NET, Microservices, Service-oriented Architecture (SOA), Elasticsearch, APIs, OpenAPI, Azure, C#.NET, Microsoft SQL Server, HTML, ASP.NET, C#, LINQ, Enterprise Architecture, Platforms, Scalability, Containers, Analytics, Test Automation, Team Management, XML, Serverless Architecture, REST APIs, Databases, Event-driven Programming, Scaling, Back-end, Kubernetes, SQL, Technical Leadership, Web Application Architecture, .NET Core, REST, Test-driven Development (TDD), Azure DevOps, ASP.NET Core, Back-end Architecture, Back-end Development, Microsoft Azure, HTTP REST, Entity Framework Core, Software Architecture, Leadership, Third-party APIs, Cloud Architecture, Azure SQL, Application Architecture, System Architecture, REST API Architecture, System Architecture Design, Technical Documentation, Diagrams, Event-driven Architecture, Distributed Architecture, .NET 4, Endpoint Security, Entity Framework, Team Leadership, GitFlow, Project Management, Agile Project Management, NoSQL, Database Design, API Integration, Real-time Data, Windows PowerShell, Transact-SQL (T-SQL), JSON Web Tokens (JWT), Web App Development, Minimum Viable Product (MVP), API Architecture, Node.js, Back-office System Development, Web Architecture, DevOps, Continuous Integration (CI), Solution Architecture, OpenAI API, Creative Problem Solving, CI/CD Pipelines, Microsoft Visual Studio, System Design, IIS, Windows Services, Legacy Software, DB, GraphQL, TypeScript, Enterprise Software, Software Project Management, Agile, Agile Software Development, Data Structures, Database Architecture
Team Leader | Technical Leader
2018 - 2018
EcoVadis SAS
- Oversaw all the activities within the team while creating its working workflow processes and cooperation methodologies with other teams.
- Designed the architecture and developed several applications while managing a team of seven developers.
- Audited, changed, and upgraded the architecture of the existing software projects, refactoring to scale-out applications.
Technologies: .NET, Software Design, Management, Architecture, C#.NET, Microsoft SQL Server, HTML, Azure, ASP.NET, C#, LINQ, Enterprise Architecture, Platforms, Scalability, Containers, Test Automation, Team Management, XML, Elasticsearch, REST APIs, Databases, Event-driven Programming, Scaling, Back-end, SQL, Technical Leadership, Web Application Architecture, .NET Core, REST, Test-driven Development (TDD), Azure DevOps, ASP.NET Core, Back-end Architecture, Back-end Development, Microsoft Azure, HTTP REST, Entity Framework Core, Software Architecture, Leadership, Third-party APIs, Cloud Architecture, Azure SQL, Application Architecture, System Architecture, REST API Architecture, System Architecture Design, Technical Documentation, Diagrams, Event-driven Architecture, Distributed Architecture, .NET 4, Endpoint Security, Entity Framework, Team Leadership, GitFlow, Project Management, Agile Project Management, NoSQL, Database Design, API Integration, Real-time Data, Windows PowerShell, Transact-SQL (T-SQL), Web App Development, Minimum Viable Product (MVP), API Architecture, Node.js, Back-office System Development, Web Architecture, DevOps, Continuous Integration (CI), Solution Architecture, OpenAI API, Creative Problem Solving, CI/CD Pipelines, Microsoft Visual Studio, Windows Services, Legacy Software, DB, GraphQL, TypeScript, Enterprise Software, Software Project Management, Agile, Agile Software Development, Data Structures, Database Architecture
Team Leader
2017 - 2018
Cybercom Group
- Managed and grew an offshore team of 3-8 developers.
- Designed the architecture and developed several applications.
- Provided technical support to the sales team by creating project requirement documentation and estimating projects' costs and duration.
Technologies: Management, Design, Agile Delivery, C#.NET, Microsoft SQL Server, HTML, Azure, ASP.NET, C#, LINQ, Team Management, XML, REST APIs, Databases, Back-end, SQL, Technical Leadership, .NET Core, Azure DevOps, Back-end Architecture, Back-end Development, Microsoft Azure, Software Architecture, Leadership, Full-stack, Full-stack Development, Cloud Architecture, Azure SQL, System Architecture, System Architecture Design, Diagrams, .NET 4, Entity Framework, Software Consulting, Razor, Team Leadership, Project Management, Agile Project Management, Database Design, Consulting, Transact-SQL (T-SQL), Minimum Viable Product (MVP), Web Architecture, DevOps, Continuous Integration (CI), Creative Problem Solving, CI/CD Pipelines, Microsoft Visual Studio, Data Processing, IIS, DB, GraphQL, Software Project Management, Agile, Agile Software Development, Database Architecture
Senior Software Consultant
2015 - 2017
Cybercom Group
- Designed the architecture and developed several applications.
- Audited, changed, and upgraded the architecture of the existing software projects.
- Improved scalability attributes of the existing applications.
- Provided technical support to the sales team by creating project requirement documentation and estimating projects' costs and duration.
Technologies: .NET, Azure, APIs, ASP.NET MVC, C#.NET, Microsoft SQL Server, HTML, CSS, ASP.NET, C#, LINQ, Web Development, XML, REST APIs, Databases, Back-end, SQL, Azure DevOps, Back-end Architecture, Back-end Development, Microsoft Azure, SOAP, Software Architecture, Full-stack, Full-stack Development, Windows Presentation Foundation (WPF), Cloud Architecture, Azure SQL, SendGrid, .NET 4, Angular, Entity Framework, Software Consulting, Razor, Database Design, Consulting, Transact-SQL (T-SQL), Continuous Integration (CI), Creative Problem Solving, Microsoft Visual Studio, System Design, Machine Learning, Data Science, IIS, .NET MAUI, Blazor, DB, Agile, Agile Software Development, Database Architecture
.NET Developer
2010 - 2013
Invent On Sp. z o.o.
- Handled core development, including analysis, design, and coding.
- Delivered software according to the clients' requirements.
- Maintained software applications within the required quality.
Technologies: .NET, ASP.NET, Databases, Microsoft SQL Server, HTML, CSS, C#, LINQ, Web Development, XML, Back-end, SQL, Back-end Development, Full-stack Development, Windows Presentation Foundation (WPF), .NET 4, Software Consulting, Database Design, Transact-SQL (T-SQL), Continuous Integration (CI), Creative Problem Solving, Microsoft Visual Studio, IIS, DB
Project History
Desta
https://desta.pl/Desta is an invoicing SaaS for Polish companies, built around KSeF, the national e-invoicing system: KSeF API v2 authentication, sending and downloading FA(3) e-invoices, and verification QR codes. It grew out of a client platform I built and maintained for an accounting company since 2017; in 2026 I rebuilt it as a product with a Laravel web app and a native Android app.
I designed and built the entire platform myself, both apps end to end, working with an accounting domain expert who advised on requirements and in-app copy. The web app runs on PHP 8 and Laravel 12 with MySQL, Tailwind CSS, Alpine.js, and Vite. It generates PDF invoices, Excel exports, and JPK_V7M and JPK_FA tax files, handles subscription billing, and integrates with the GUS REGON registry, EU VIES, and NBP exchange rates. The Android app is written in Kotlin with Jetpack Compose, Room, and coroutines and talks to KSeF directly. Both are covered by more than 2,000 automated tests (PHPUnit, JUnit, MockK) and monitored with Sentry.
I designed and built the entire platform myself, both apps end to end, working with an accounting domain expert who advised on requirements and in-app copy. The web app runs on PHP 8 and Laravel 12 with MySQL, Tailwind CSS, Alpine.js, and Vite. It generates PDF invoices, Excel exports, and JPK_V7M and JPK_FA tax files, handles subscription billing, and integrates with the GUS REGON registry, EU VIES, and NBP exchange rates. The Android app is written in Kotlin with Jetpack Compose, Room, and coroutines and talks to KSeF directly. Both are covered by more than 2,000 automated tests (PHPUnit, JUnit, MockK) and monitored with Sentry.
Stemma
https://bfrackowiak.pl/stemma/Stemma is an architecture modeling tool for solution and data architects in which the source code is the model. Bounded contexts, capabilities, containers, data flows, dependencies, decisions, and risks live in a C# model versioned in Git. Every change made on the canvas becomes a Roslyn rewrite of real .cs files, so the git diff contains only the intended change, the diagram cannot drift from the code, and humans and AI agents can edit the same model through reviewable diffs.
I designed and built it end to end: the Roslyn round-trip engine, the ASP.NET Core back end, and a React 19 canvas with audience-specific views, story books, and a single-file HTML report export. It ships as a .NET tool with CI and sample workspaces, including a model of Stemma's own architecture.
I designed and built it end to end: the Roslyn round-trip engine, the ASP.NET Core back end, and a React 19 canvas with audience-specific views, story books, and a single-file HTML report export. It ships as a .NET tool with CI and sample workspaces, including a model of Stemma's own architecture.
Builder for the Future
It is a platform dedicated to architects and building engineers to engage and share local construction sites. The platform includes modules for managing events, contests, surveys, mailing, users, and certificates.
I was responsible for the system design and execution, from prototyping with the client to implementation and production. I also have been in charge of its maintenance since April 2017.
The platform hosts 100 thousand users and registers 500 daily active users.
I was responsible for the system design and execution, from prototyping with the client to implementation and production. I also have been in charge of its maintenance since April 2017.
The platform hosts 100 thousand users and registers 500 daily active users.
Education
2013 - 2017
Doctoral Studies in Software Engineering
University of Warsaw - Warsaw, Poland
2008 - 2013
Master's Degree in Computer Science
Nicolaus Copernicus University - Toruń, Poland
Certifications
JANUARY 2014 - PRESENT
Functional Programming Principles in Scala
Swiss Federal Institute of Technology Lausanne via Coursera
JANUARY 2013 - PRESENT
ITA105 Object-Oriented Programming
Microsoft IT Academy Programmer
JANUARY 2010 - PRESENT
SPSS Technology Junior Expert
IBM
Skills
Libraries/APIs
OpenAPI, REST APIs, Entity Framework, OpenAI API, LINQ, Node.js, Apache Lucene, React, MockK
Tools
Visual Studio, Microsoft Visual Studio, Claude Code, GitHub, SendGrid, JetBrains Rider, Roslyn, Sentry
Languages
C#, C#.NET, SQL, Transact-SQL (T-SQL), HTML, XML, GraphQL, Java, Scala, HTML5, CSS, XAML, JavaScript, PHP, TypeScript, Kotlin
Frameworks
.NET, ASP.NET MVC, ASP.NET, .NET Core, ASP.NET Core, Entity Framework Core, .NET 4, Bootstrap, Windows Presentation Foundation (WPF), Windows PowerShell, JSON Web Tokens (JWT), Laravel, .NET MAUI, Blazor, Angular, Razor, Tailwind CSS, Alpine.js, PHPUnit
Paradigms
Agile, Object-oriented Programming (OOP), Management, Service-oriented Architecture (SOA), Microservices, Microservices Architecture, Web Application Architecture, REST, Back-end Architecture, Application Architecture, REST API Architecture, Event-driven Architecture, Agile Project Management, Database Design, API Architecture, Web Architecture, DevOps, Continuous Integration (CI), Agile Software Development, Event-driven Programming, Test-driven Development (TDD), Azure DevOps, Model Context Protocol (MCP), CQRS, Functional Programming, Test Automation, Serverless Architecture
Platforms
Azure, Linux, Windows, Visual Studio Code (VS Code), Windows Server, Software Design Patterns, Kubernetes, Xamarin, Android
Storage
Databases, Microsoft SQL Server, Azure SQL, DB, Database Architecture, PostgreSQL, Elasticsearch, MySQL, NoSQL
Industry Expertise
Project Management
Other
Software Development, Architecture, Software Design, Distributed Systems, APIs, Design, Web Development, Back-end, Technical Leadership, Back-end Development, Microsoft Azure, HTTP REST, Software Architecture, Leadership, Third-party APIs, Full-stack Development, System Architecture, System Architecture Design, Technical Documentation, Distributed Architecture, Software Consulting, Team Leadership, GitFlow, Consulting, API Integration, Real-time Data, Web App Development, Minimum Viable Product (MVP), Solution Architecture, Creative Problem Solving, CI/CD Pipelines, System Design, IIS, Windows Services, Legacy Software, Enterprise Software, Software Project Management, Data Structures, Domain-driven Design (DDD), Azure Service Bus, Agile Delivery, Low-latency Software, Concurrency, Enterprise Architecture, Scalability, Team Management, Scaling, Full-stack, Cloud Architecture, Diagrams, Endpoint Security, Microsoft Graph API, Back-office System Development, Data Analysis, Platforms, Integration, Machine Learning, Data Processing, Data Science, Agentic AI, Large Language Models (LLMs), Generative Artificial Intelligence (GenAI), AI Agents, SaaS, Statistics, HTTP Server, Containers, Analytics, SOAP, Travel, RESTful Microservices, Data Architecture, Jetpack Compose, Room
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