Krzysztof is available for hire
Hire KrzysztofKrzysztof Kwiecień
Verified Expert in Engineering
Software Development Developer
Berlin, Germany
Toptal member since December 2, 2020
Bio
Krzysztof is a versatile, experienced software engineer passionate about creating scalable, high-performance web applications. He has a proven track record of leading teams, managing programs, and delivering exceptional results across diverse fintech, B2B, and B2C industries. With expertise in various technologies, Krzysztof excels at translating business needs into innovative technical solutions and consistently exceeds client expectations.
Portfolio
Klarna
Engineering Management, React, Amazon Web Services (AWS), Docker, TypeScript...
Deloitte
Engineering Management, Delivery Management, React, Amazon Web Services (AWS)...
Deloitte Digital
SCSS, Azure, Salesforce, Software Evaluation, Recruiting, CSS, HTML, Express.js...
Experience
- Software Development - 10 years
- JavaScript - 10 years
- Node.js - 6 years
- React - 6 years
- TypeScript - 5 years
- Amazon Web Services (AWS) - 5 years
- Engineering Management - 4 years
- Software Architecture - 4 years
Availability
Part-time
Preferred Environment
Git, MacOS, Visual Studio Code (VS Code)
The most amazing...
...experience was seeing my mentees at Deloitte and Klarna flourish, growing into confident senior and lead engineers.
Work Experience
Engineering Manager
2022 - PRESENT
Klarna
- Orchestrated the rollout of Express Checkout across a payment platform serving millions of customers, achieving an increase in purchases and expanding merchant adoption to thousands of merchants within six months through carefully phased deployment.
- Drove cross-functional program delivery through daily collaboration with multiple domain teams, translating business vision into executable technical programs that resulted in a $200+ million processed payment volume.
- Created and maintained program dashboards tracking key metrics, including session volume, conversion rates, and merchant adoption, leading to 40% faster issue detection and resolution during rollout.
- Scaled technical programs to handle 2+ million monthly sessions while maintaining 99.999% availability, with less than five minutes of monthly downtime through comprehensive monitoring and alerting systems.
- Managed program risks through systematic analysis of 200+ merchant edge cases and requirements.
- Contributed to the promotion of six engineers to senior and lead roles.
- Managed engineering delivery in three teams, leading and mentoring 15 engineers, including engineering managers and staff engineers.
- Spearheaded the JavaScript hiring process, conducting both behavioral and system design interviews.
- Led cross-domain initiatives and contributed to unifying Klarna's APIs and credentials, wrote and reviewed API change documents, prepared implementation plans, and executed parts of them.
Technologies: Engineering Management, React, Amazon Web Services (AWS), Docker, TypeScript, Node.js, Jenkins, System Design, Front-end, Back-end, Software Architecture, JavaScript
Engineering Manager
2021 - 2022
Deloitte
- Crafted a visionary 3-year strategy for the front-end/Salesforce developers team, aligning technical initiatives with business goals.
- Nurtured a team of seven software engineers, implementing personalized growth plans that resulted in two engineers advancing to the next level.
- Established and cultivated a thriving partnership with one of the largest clients from the US, leading to an impressive extension of our initial engagement by an additional year, with an increased team size to support the collaboration.
- Introduced a successful mentoring program, enhancing junior developers' skills and fostering a culture of continuous learning.
Technologies: Engineering Management, Delivery Management, React, Amazon Web Services (AWS), TypeScript, Node.js, PostgreSQL, Angular, GraphQL, Front-end, Back-end, Software Architecture, JavaScript
Full-stack Developer
2018 - 2021
Deloitte Digital
- Developed a React-web application integrated with SharePoint. Helped design and implement a dashboard, presenting detailed information regarding each funding application.
- Implemented HTML and CSS3 for desktop, tablet, and mobile with Qlik-data integration. Built an interactive tool capable of achieving the overreaching goal of aid transparency.
- Helped with the full-stack development for medical affairs and vaccines departments. Worked with Angular 7 and Node.js connected with the MySQL database.
- Developed an Angular app hosted on Azure, used to facilitate calculating the needed amount and type of tools for a particular drilling project.
- Designed a front-end architecture for a React web app, Next.js email template builder, and a platform to utilize these templates for one of the FAANG companies. Led a team of eight front-end developers on these two streams.
Technologies: SCSS, Azure, Salesforce, Software Evaluation, Recruiting, CSS, HTML, Express.js, TypeScript, Redux, RxJS, Microsoft SQL Server, Node.js, React, Angular, JavaScript, Amazon Web Services (AWS)
Rollout Consultant
2016 - 2018
BSH Hausgeräte
- Contributed to the implementation of IT solutions in the fields of WCMS, eCommerce, and customer service.
- Provided business and technical support to corporate and regional customers.
- Maintained the problem documentation and managed the knowledge library.
- Carried out on-site technical training for 30 people from many different countries.
Technologies: Confluence, Jira, CSS, HTML, JavaScript 6, React, eCommerce, Testing, E2E Testing, Project Management, JavaScript
Web Developer
2014 - 2016
Accenture
- Developed the front end of a crucial part of the CRM 360 dashboard view for users.
- Improved the client's existing front-end JavaScript framework.
- Developed a platform that connects insurance companies, garages, and vehicle owners. The app suggested cheaper replacement parts for users.
Technologies: Frameworks, PostgreSQL, AngularJS, Spring Boot, Jakarta Server Pages (JSP), CSS, HTML, JavaScript
Experience
Dashboard for Investment Banking Clients
An app made for a German investment bank. It shows the current state of an application that the users raised. I created only the front-end part since SharePoint was used as a back end.
React with Redux and TypeScript were used to speed up the development and create a library of reusable components that the client might use to extend the app.
React with Redux and TypeScript were used to speed up the development and create a library of reusable components that the client might use to extend the app.
First Point of Contact App for a Manufacturing Sector Client
The aim of developing this app was to digitize one step in the process of buying tools. Interactive and animated forms were used to make it more user-friendly and appealing. I created the app from scratch, including its front end, back end, and data layer.
Intranet for a Consulting Company
Developed an app that integrates data from many different systems that the clients can use and show appealingly. It also enables users to change the data while respecting all the client's business rules and policies.
Website for a Medical Clinic in Poland
Built a new website for a medical clinic based in Warsaw, Poland, called Przychodnia i Endoterapia Polskiej Fundacji Gastroenterologii.
The website includes pages for all the clinic's services, doctors who work there, and other various data essential to the patients. The traffic has increased by 15% since the new website was introduced.
The website includes pages for all the clinic's services, doctors who work there, and other various data essential to the patients. The traffic has increased by 15% since the new website was introduced.
Education
2013 - 2017
Bachelor's Degree in Computer Science
Warsaw University of Technology - Warsaw, Poland
Certifications
APRIL 2022 - APRIL 2025
AWS Certified Cloud Practitioner
Amazon Web Services
OCTOBER 2018 - PRESENT
Agile Project Management Foundation
APMG International
Skills
Libraries/APIs
React, Node.js, RxJS
Tools
Git, Jira, Confluence, Webpack, Jenkins
Languages
JavaScript, HTML, CSS, TypeScript, SCSS, JavaScript 6, GraphQL
Frameworks
AngularJS, Angular, Jakarta Server Pages (JSP), Spring Boot, Redux, Express.js
Paradigms
Agile Project Management, E2E Testing, Testing
Platforms
Amazon Web Services (AWS), MacOS, Salesforce, Azure, Visual Studio Code (VS Code), Docker
Storage
PostgreSQL, Microsoft SQL Server
Industry Expertise
Project Management
Other
Software Development, Front-end, Software Design, Software Architecture, eCommerce, Recruiting, Engineering Management, Back-end, Software Evaluation, Gatsby, Frameworks, Delivery Management, System Design
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