CALLSTACK experts

Market analyst and super specialist in finance. Passionate about numbers - all financial indicators (and not only ones) are always at her fingertips. She loves challenges and nothing is impossible for her. A great lover of sports and plants, who spread good energy and a dose of motivation every day.

Co-Founder & Supervisory Board Member.

As the CEO of Callstack, Kris brings in more than two decades of experience in multinational organizations, where he held several senior management positions in general management, sales, business & corporate finance advisory. His career includes successful leadership of major change management and transformation programs as a Senior Executive, CEO, and Supervisory Board Chairman. In his leisure time, Kris enjoys sharing his knowledge as a meditation teacher.

Krzysztof helps companies to choose well-suited cross-platform development solutions. Backed by IT Operations and IT Project Management background he oversees the whole process from defining needs to implementation to make it hit your business goals!

Head of Operations overseeing, ensuring top-notch services and transforming CK operations area (Project Management, Quality Assurance, Resource Planning, and Delivery) with over 18 years of professional experience from international organizations and Big 4 consulting in operational transformations, Target Operating Models, change management, process excellence, and strategy development. In his free time, Michał is into crafting furniture, jogging, riding a bicycle, and spending quality time with his wife, kids, and two dogs.

Head of Technology overseeing Callstack's Open Source and R&D efforts. Making sure we keep on innovating in app development space. Passionate about building OSS tools for JS devs. Created React Native Testing Library. And he likes rockets!

Co-founder & Supervisory Board Member.

Primarily responsible for planning and implementing strategies that will attract, engage, and develop employees. His main goal is to create and maintain people focused high-performance Callstack culture, where people are satisfied and engaged. He is known for providing practical support quietly and conscientiously, usually behind the scenes. Fan of photography, cycling, American history and development books. Father of two Teenagers and recent enthusiast of Berlin Halfmarathons.

Head of Marketing at Callstack with experience in B2B marketing and sales enablement. In his work he combines data with creativity.

Leading and growing an Account Management Team at Callstack. Focused on ensuring we provide the best customer experience and consulting value to our partners. Adventure seeker and travel lover, enjoys exploring new places, cuisines and cultures.

As an HR Business Partner, Adka provides a support for Callstack management and employees in all activities undertaken in the field of human potential management. Focused to handle everything from onboarding and benefits to compliance and employee relations. A big fan of Insights Discovery model, working intensively on implementing it to our company. :) Passioned about traveling and a big coffee lover!

Full-stack developer with years of experience in building web apps with React. In love with everything around JavaScript and a big fan of serverless. Productivity geek, enjoying learning in any form. Interested in all things: React, Jamstack & serverless. Started programming to create a (yet another) social media platform.

JavaScript developer focused on enhancing his skill set every day. Passionate with learning and getting to know new technologies.Mentor in the field of Mobile Architecture at Callstack.Privately, a rollerblades master, concert enthusiast and foodie 😋.

QA Automation Engineer with years of experience in testing software on different levels of test pyramid. Experienced in web and mobile apps testing. Participated in automotive, financial, logistic projects. Basketball fan.

Project Manager responsible for the successful delivery of the project. She appreciates the uniqueness of people and believes that together we can achieve more than alone. A fan of well-organized processes and organising things in such a way that they are not as overwhelming as they may seem. If she had to choose one (the only) program she would use for the rest of her life, it would probably be Excel. Enjoys good books, long walks and spending time with loved ones.

React Native Developer passionate about building mobile apps with experience in web app development.Interested in Blockchain and Web3. A big fan of traveling, cycling and specialty coffee.

HR Business Partner with the motto "People first”. The user of coaching and advisory methods in HR to develop employees. Discovers a person's hidden potential and talents and cares for work wellbeing. Psychometrist. Enthusiast and participant in the holistic school of psychotherapy. Fan of blues and guitar jazz music. Reader & books writer.

Self-taught developer with a passion for new technologies and innovation. Her first website used Flash and her first paying developer job required jQuery, but since she has enthusiastically adopted React and React Native. Ola enjoys watching sit-coms and reading all sorts of books.

Always smiling office manager who deals with business documents and correspondence, supplies management and takes care of the office space to be the best place to work! She is a dog person, currently teaching her adopted dog Max how to survive in the urban jungle. Ola loves sports too, especially softball and yoga.

Senior Content Marketer focused on delivering value and sharing knowledge. When creating any form of content, whether it's an expert guide, a case study, or a webinar, she seeks to uncover and address the recipients’ needs and pain points. Passionate about creating user-centric content that guilds bridges between the brand and the clients. After hours, she draws, embroiders, cooks.

IT Sourcer responsible for finding new Callstackers - developers for our company. Passionate about employer branding activities, employee satisfaction surveys, and candidate experience. Privately, a lover of traveling and cooking.

Project manager focused on the successful delivery of the project. Several years of experience in IT companies. Value the most open communication and positive atmosphere. Privately photographer, passionate about travels, psychology and criminal books.

An anthropologist by education with a passion for HR. Has ten years of professional experience in the HR field, gained in various sectors and in various functions. Her role is to support the business in achieving strategic goals by implementing HR solutions and recommending appropriate actions. A certified DISC D3 consultant. An owner of a one-year-old beagle who has changed her world and increased time spent on walks.

Previously a full stack software developer focusing right now more on web and mobile development. Loves to tinker with code and learn how it all works. Frequently experiments with new technologies. Passionate about OSS and tries to contribute frequently. Used to play clarinet in a philharmonic band, and also plays the bass guitar.

HR Administrator with a helping hand, always ready to support all the Callstackers. She takes care of typical duties including managing various HR documents, updating them, keeping a track record of personnel data, managing payroll, answering employees’ questions and helping new hires get inducted into our workforce. In her free time, Angelika likes hiking or watching classic films.

Finance and Administration Specialist with few years of experience in accounting and analysis. Interested in development in the field of controlling and reporting, she’s willing to become an Excel expert. Anna loves trekking and climbing, and her big dream is to own a little house in the mountains :)

Self-taught developer, who is a fan of React Native. Anna likes learning and developing herself. Has switched her profession from the Languages Studies to Software Development, so JavaScript is like a foreign language to her. ;) She loves painting and trying new art techniques.

Former IT Senior Project Manager with 9+ years of experience both in large multinational corporations and SMBs. Currently expanding his business expertise and utilizing networking skills in the Account Management Team. Based on his background, loves working with all sizes of customers on complex, strategic accounts. Has a knack for problem-solving and enjoys creative brainstorming. After hours amateur basketball player, with a passion for sitcoms, podcasts and tattoos.

Senior React-Native Developer, passionate about mobile technology, started as a backend developer in ASP.NET. Focused on learning new technologies and improving his skillset. Always looking for new challenges. Creator of SmartWorkout app for powerlifting and bodybuilding. Loves board games and gym.

Her mission is to build solid relationships and increase the company's visibility in the React Native Community. She's the brain behind our biggest event, the React Native EU conference, our podcast, and all activities with and for the Community. When there is free time, it's sport-time - Barbara is a great fan of wakeboarding, kitesurfing, roller skating, and HIIT workouts.

Bartosz is experienced in embedded systems and automotive infotainment, but his passion for application's development quickly led him to React Native. Maintainer of @react-native-community/slider and some web browser's add-ons, but in his spare time he also contributes to .NET documentation. His field of interest are Web browser's add-ons and extensions.

Originally Fullstack developer who fell in love with frontend and React. Now working with React Native as a natural consequence of growing. Loves to ride on one of his five bikes and reading.

JS developer with multiple years of experience,  in love with React. He has a good eye for design details, implements features with respect to time and budget. Also interested in UX to develop apps with simple but powerful user interfaces. Interested in React and React Native ecosystem. He’s a metalhead in the deep of heart, fan of fantasy and personal growth.

Developer with years of experience in building client & server-side applications. Mesmerized by JS and React ecosystem. Always focused on building robust and magnificent apps with great care about their architecture and performance. Interested in an Open Source software. If not coding, then most likely he's on a kart track or brewing a perfect shot of espresso.

RN developer passionate about creating reliable, intuitive, and aesthetically pleasing code. Highly motivated to tackle challenging problems and come up with innovative solutions. Contributor to React Native Builder Bob. Focused on making well-documented & robust software. Mostly interested in computer graphics, low-level programming, and efficiency. He uses vim on a daily basis.

A Software Tester with years of experience in testing desktop applications. Passionate about delivering applications that meet all customer expectations. Loves well-written documentation. :)

Mobile QA tester since early 2019 with experience in automated testing using Java with Appium. Always on the lookout for learning new skills. Can’t stop seeing bugs after work either… Besides, he's a huge enthusiast of language-related topics, music production and retro RPGs.

Frontend engineer & tech enthusiast with over 7+ years of professional experience in web and mobile app development, with a good sense for writing sustainable code and problem-solving. Mentor in the field of Advanced Web development at Callstack. Spends his free time riding all kinds of boards, drinking yerba maté and going on adventures with his doggie. If you see him, usually there's an Australian Shepherd called Eugene nearby somewhere :).

A Software developer with 6 years of experience building various web and mobile applications, passionate about delivering a good user experience. Enjoys solving challenges with React, React Native, and TypeScript. Creator of React Native library with over 300 stars on GitHub: react-native-dark-mode. Besides, Dimitar is a huge Pokémon fan.

Software Engineer who enjoys challenging problems to make our world a better place. Creates cross-platform mobile applications with React Native, and helps other companies to migrate their native apps. Enjoys studying C++ and apply it in his pet projects.

RN developer with years of experience in web and native Android apps. Loves building a delightful frontend and always keeps in mind user experience. Cares a lot about code readability and project structure. Thrives when working as part of a team. Currently, mostly focused on building performant apps. A huge fan of Witcher, Harry Potter and Marvel. - You name it. :)

React-Native Senior, with 12 years of experience in Mobile development, working with Android, Flutter, RN,  iOS and Unity. Collaborator of react-native-paper OSS library. Looking forward to make readable and maintainable code. Built a Mobile app with 6-digit revenue! He likes doing sports and dancing.

QA Automation Engineer with experience in automating web and mobile applications. Fascinated by topics related to performance tests and security tests. A long-time volunteer who likes to share knowledge and infect with enthusiasm for programming.

An avid JavaScript developer. Started off building for the web and now focuses in building native mobile apps with React Native. Currently specialising in frontend architectures, performance, and animation related topics. Eto is passionate about creating intuitive user experiences and solving problems. Interested in Native Mobile Languages and Machine Learning. Having a mixed fun interest of gaming, playing football and making music.

React Native Developer with 5+ years of experience in software and mobile development. Very meticulous and concerned about the quality of the code and the product, always looking for the best solutions to the clients. Deeply interested in mobile and project architecture, and now also wants to engage more with the community. In his free time he likes watching movies / series, learning new things and playing video games when possible.

Frontend developer passionate about exploring every aspect of JavaScript. Always willing to learn new technologies. Big fan of React and Redux.

Senior Frontend Developer with years of experience in building mobile and web solutions in multiple frameworks and libraries (React Native, React, Next.js, Ionic, Angular.js, Angular 2+, C# MVC .Net). After mastering web development, he’s become passionate about building beautiful and neat mobile solutions in React Native. Mr Gadget. Passionate about cutting edge technologies.

Senior Content Marketer who takes care of content creation, distribution, and promotion in line with the best SEO and SEM practices. She's always on the lookout for new ideas and promotion strategies. Whenever possible, she does her aerial hoop classes and explores new places from her bucket list.

Tech Consultant with over five years of experience in supporting startups and enterprise companies with a background in web development and FinTech. Passionate about building backend services and FinTech apps. Can help with Python, Django, Docker, AWS, and FinTech Infrastructure. Stripe Certified Professional Developer. Loves to travel and dance.

A seasoned software engineer with years of experience working on numerous projects for international clients. React and React Native enthusiast with a professional attitude who can contribute not only with his coding skills but also with his decision-making, protectiveness and critical thinking. Time management, punctuality and commitment are part of his core principles. Graduated with a Bachelor of Computer Science from the University of Liverpool with a first-class degree. Loves dogs!

TypeScript enthusiast mastering the React Native, Android & iOS realm. He feels best in diving deep with mobile tech to explore the underlying concepts, making proof-of-concept projects, and experimenting with new technologies. IA contributor to RN core and co-founding his pet project POETRY on play store. Loves to play FIFA and read books in his free time.

Frontend developer with a deep affection for React. Having worked with the web for the majority of his career, he eventually succumbed to the temptations of React Native. Loves music and cats.

JS developer who started his journey as a Front-end dev, specialized in React and React Native. Big supporter of Blockchain Technology and web3 world with prior experience in building different kinds of web and mobile apps from E-banking to NFTs Platforms. Always trying to follow best practices and paying attention to details. Creator and Maintainer of eslint-plugin-security-node library. When not coding, he likes to play techno music on his decks.

A dedicated developer who puts a lot of attention on details in every task that he does. Always committed and eager to learn. Likes to create things and dive into how they work. He’s interested in improving not only app performance, but also automating routine tasks and increasing work efficiency. Mentor in the field of Performance and DevOps at Callstack. A father of two and a husband of a woman of his life. Those two roles give him strength to move mountains. He has been training the Wim Hof method since 2019 so "Cold is his real warm friend". ;)

With multiple years of delving deep into React.js development in his pocket, Kuba went on to master the mobile development next. Passionate about edge technologies, clean and minimalistic code and charting the paths for the future of React and React Native development.

Software Developer working at Callstack since the very beginning. After mastering web, he moved to React Native. Responsible for leading Delivery Team and technical recruitment. A fan of leadership as a partnership.

Software developer with a passion for React & React Native who loves to dissect and analyze every problem he encounters in his work. He has a particular interest in performance optimisation, tweaking and fine-tuning for optimal results. Enjoys hiking in rugged, scenic regions such as Scotland or Iceland.

Jakub is responsible for establishing relationships with new clients and introducing them to React Native technology. Besides sales, Jakub's passions include riding a bike (preferably on a bikepacking trip), sports like basketball or volleyball and video games.

Young developer with years of experience building React Native apps for both Android and iOS platforms. Crazy about usage of the newest technologies, setting new best practices and improving each and every day. Interested about brownfield systems and performance optimisations. Privately, a high altitude mountaineering enthusiast, aiming to complete Seven summits challenge. As he says: "Born to win. Win big. To live hard and train hard".

Senior RN Developer with rich background: started as a .NET developer, through Full-stack to building mobile apps. Passionate about start-ups, learning about business and creating apps that can have a real impact on people using them. Coordinated and designed an architecture of a project that synchronizes data of different formats between companies' all over the world, using Azure cloud. An owner of 3 cats and 2 dogs, which results in the greatest evening in-house theater you can get!

TypeScript and React Query fan. Pair programming enthusiast. Stripe Community Expert and occasional OSS contributor. Mentor in the field of Newcomers onboarding at Callstack. Helped reduce shared bundle size by 50% from 560kB to 280kB and boost performance of a large e-commerce. All year biker and tea connoisseur. Cosplaying as a sysadmin. Also owned 20 hamsters as a child.

IT Sourcer responsible for searching experienced React Native Developers and QAs. Passionate about copywriting and recruitment data analysis. After work, a dachshund's mama, interested in true crime documentaries and stand-up comedy. Besides, she's a soul and R'n'B music lover always ready to dance ;).

Experienced manager, who believes in people and their potential to grow. She is skilled mainly in the area of recruitment, employer branding and communication. She gained her experience both in the corporate-, product related- and software houses environment. A huge fan of work-life balance and remote-first approach. When not working, she is most probably playing tennis or spending valuable time with her family and friends.

Newest office coordinator full of enthusiasm and meticulousness learned from experience in the hospitality industry. In his free time passionate about crystals, zodiacs, self-improvement, and the architectural history of our lovely Breslau.

React Native Developer who pays attention to details. Focuses on finding the simplest yet best solutions. Loves minimalistic design with great UX. He is always ready to improve his skills and take on new challenges. Kacper contributed a lot to react-native-pager-view (e.g. added new architecture support).

​Self-taught developer with an e-commerce background, passionate about React and React Native. When not coding, spending way too much time working on old cars.

Mobile developer with short BI past. Solution and product oriented, loving smooth processes, startups, good atmosphere and well-written tests. Digitized processes in bicycle shop leaving hand-writing in the notebook in the past. When not at computer - spending time with loving family and outside as much as possible.

QA Engineer with almost 10 years of experience. Continuously developing his skills in new areas and by using different tools.

JavaScript expert with experience in mobile and web apps development. Has a can-do attitude, loves to solve complex problems and automate things. Passioned about building robust solutions and cares about the developer experience. Interested in functional programming and cross-platform development. Vim enthusiast and keyboard geek.

Kasia translates HR as Human Relations. A big fan of people and their hidden potential. She supports Callstack team in well-being, skills development as well as operational tasks and retention strategies. She also leads HRBP & Admin Team.

Recruitment Specialist, responsible for conducting end to end recruitment processes. Focused on bringing new  IT talents to the Callstack team. Passionate about graphic design (always with a cup of morning coffee in hand) and sailing.

Resource Planning Expert with finance and controlling experience. While using her analytical mind and natural grasp of numbers at work, after hours, she tries to explore her creative side in various DIY projects. Privately a crazy cat mommy and F1 enthusiast.

Ambitious IT Project Manager with big dreams. Responsible for overseeing all aspects of project planning and execution using her coordination, leadership, and motivational skills. Experienced with Scrum and Kanban with a broad understanding of the principles and objectives of these frameworks. An active member of PMI Poland, responsible for the Facebook and Linkedin communication. She loves snowboarding in winter and canoeing in summer.

Started his career as a tester, and slowly shifted his skills into programming. He worked on plenty of startup projects, usually as solo frontend, or with small team. His biggest achievement is becoming front lead in one of the projects. Personally, he loves 3D graphics, games, special effects, photo and cinematography. Tried himself as rock band vocalist, english standup performer, an improviser and Youtuber. Jack of all trades, master of none. Recently got a bit obsessed with AI.

IT Administrator skilled at managing networking systems, maintaining security systems, updating hardware and software, and managing databases. Passionate about technology and cybersecurity. Always looking for the opportunity to learn and develop new skills in ITSM and security to stay ahead of constantly changing cyber threats. A warm weather enjoyer, always trying to take advantage of it and ride his bike, hike, or sip a good craft beer.

A JavaScript, React  and React Native enthusiast. Ambitious, adventurous and assiduous. Eager to learn new things everyday and passionate about new technologies. Started his career as a PHP Backend developer. He loves long walks in nature.

An expert with years of experience in building native iOS and Android apps. Passionate about building delightful & well-architected mobile apps. Enjoys cooperating with clients and enabling dev teams to effectively deliver high-quality software. Likes to learn and share his knowledge about all things RN: TypeScript, best practices, new architecture, testing, performance, etc. Maintainer of React Native Testing Library & Reassure OSS projects. Likes to travel and take photographs, favorably travel photos.

Responsible for web design & development, and all marketing materials for Callstack and React Native EU conference. A great cinema, wine and travel lover. Cofounder of Kino na Trójkącie and Wina i Kina - cinema related initiatives.

Full-stack developer by heart, now specializing in React/React Native & frontend architectures. He loves to understand how things work - whether it is code, or your business. Became a Mentor for web architecture fields at Callstack and loves sharing knowledge with people. A big fan of Rust, that hopes it'll change development environment forever for a faster & more reliable software.An animal lover! You can ask him anything about our more scaly friends. :)

JavaScript developer specializing in React, always curious and excited to learn new things.

Low-level C++ developer and ex- gamedev that got hooked on mobile apps development. Passionate about hacking, optimization and learning new things. He also believes that software development is a form of craftsmanship. Made an app that renders the whole Vice City in only 1 draw call. Likes to apply minimalism to almost everything.

Software QA Specialist, most experienced in web and mobile application testing. When not bug hunting, she enjoys exploring new places and reading books. Some say she’s a pastry addict - a Cookie Monster in a tiny body! ;)

Marta is a data-driven Marketing Campaign Lead with years of experience growing organic traffic and conversions. She believes in constant improvement and innovation. Always on the lookout for new ways to promote and distribute our articles, podcasts, and e-books. She prefers chats over phone calls and long treks in the mountains over the hectic city pace.

As a part of HR team mainly responsible for moving candidates through the recruitment processes smoothly and building the best Callstack team. Always excited about meeting new people. In less than 2.5 years at Callstack, witnessed the expansion of the team from 40 to more than 130 people. Passionate about dancing, going to the gym and traveling.

A Recruiter with several years of experience in HR, specialized and focused on IT recruitment for over 5 years. Passionate about creating the most friendly and informative recruitment processes. Also interested in the basics of programming. Conducted and facilitated retrospective sessions for non-technical departments in the process of introducing scrum to the company. In her free time Martyna is passionate about DIY.

Bringing some extra energy to the Marketing team. Currently responsible for making the React Native EU 2023 conference an epic event. Hard-working, proactive, and excited when new projects arrive. He loves butter, sampled music, and the Himalayas.

JavaScript developer with a passion for web and mobile development, always eager to learn new technologies. Personally, bookwarm and a gym addict.

QA Engineer passionate about automating tests. Mateusz likes weightlifting in his free time.

Started working as a QA in 2017. Has an experience in the automotive, financial, medical, and e-commerce fields. In his past, Mateusz tested a progesterone measurement device for the Federal Ministry of Health and new and prototyped Audi and Porsche vehicles. Fun fact: he likes Star Wars and does not drink alcohol :)

JavaScript developer passionate about web and mobile development. Working with almost all major frameworks. Focused on React, React Native and Node.js. Fan of functional and reactive (RxJS) programming.

Employer Branding Specialist with the wide range of experience in HR as IT Recruiter, HR Admin but also Hotel Manager. Passion to great communication, IT industry and wellbeing trends led her to current position. Always in the heart of everything, ready to help and take up the hardest cases. Inspired by people and situations. Celebrates great childish enthusiasm in her everyday. A dog lover who became a cat mom by accident.

A front-end software developer focused on producing robust, functional and intuitive software, mostly working in React and React Native. Highly committed to code quality, has an eye on details. Her strong point is being highly self-motivated, with a strong passion to learn and grow. Focused on developing in field of native mobile development to improve her React Native experience. Her great passion for life is cycling. Gosia takes part in professional cycling tournaments and enjoys every race, no matter what her final score is.

Test engineer with JS based test frameworks background. Interested in improving testing process. He loves to play board games in his free time.

JavaScript developer with background in web development. Working mostly with React and React Native now, but always keen on learning new technologies.

Has an experience in working in both: front and back-office. Feels better with spreadsheets, but always there to help with invoices, payments, and paperwork. Likes multitasking and ad-hoc tasks, but also appreciates the regular cycle of financial work. Trying to become a spreadsheet hero. A cat person who loves to cook - everything tastes better with cat hair in it! ;)

Senior IT Project Manager with hands-on experience in complex projects delivery. Believes that transparent communication is the key to success. As the System Engineer, she prides herself on an analytical mind with excellent problem-solving skills. In her spare time, she either teaches ballroom dancing or flies in a wind tunnel.

Frontend developer passionate about mobile development with React Native. Always excited to learn new technologies and work with native mobile languages. Cares deeply about good looking interfaces and great user experience. Loves music and Arsenal F.C.

PM with a customer-centric approach. She understands the importance of teamwork and always lives up to her commitments. While focused on the day-to-day tasks, she ensures that the project's goal and mission are always remembered. Used to present live demos in front of big audiences, so she's always open to public speaking challenges. Besides work, she enjoys rollerblading, skiing, and dance classes, which help her stay active all year.

Software Engineer with almost 6 years of development. Working a lot in outsource, with big and small clients, mostly in React and React Native. Like to write code and playing around with new technics and technologies. Got master of technical sciences in the university. In his free time, Nikolay is playing football, going to gym, and playing CS:GO.

Experienced Event Manager, Party Girl. She is responsible for organizing our internal events and co-creating React Native EU Conference. Passionate about travels, food, and pole dancing. A happy soul.