config-driven-testimonials demo
by Kostiantyn Keilin, Senior Software Engineer
This is a demo of my pet project: a fully configurable testimonials widget. Every field you see — layout, colors, content, animation — is driven by a config. Use the panel on the left to generate your own configuration and see changes in real time. 💬 The testimonials shown are real reviews from real people I've worked with. If you'd like to collaborate — feel free to connect.
“I had the pleasure of managing Kostiantyn at EPAM, and my experience working with him has been entirely positive. He consistently fulfilled all responsibilities assigned to him with a high level of quality and professionalism. Kostiantyn provided thoughtful feedback both on project matters and during the technical interviews he conducted. He is always positive, focused, and approachable, with a strong ability to learn new technologies quickly while maintaining a broad technical expertise. Throughout our collaboration, there was not a single instance where he missed a deadline — if he committed to completing something by the end of the day, that's exactly when it was done. I can wholeheartedly recommend Kostiantyn as an excellent developer, colleague, and team player.”
Feb 19, 2026— Preeti Indulkar
Manager21 yrs exp“I conducted an internal interview with Konstantin for a project, and he left a very positive impression. He comes across as a knowledgeable specialist with a solid technical background and a deep understanding of software development. At the same time, he's an open and friendly person with extensive hands-on experience and a broad view of modern technologies. The conversation flowed naturally, and we were on the same wavelength throughout. I'd be glad to have an opportunity to work with him on a project in the future.”
Feb 11, 2026— Manoj Sharma
Colleague8 yrs exp“I had the great pleasure of working with Konstantin Keylin in the same company, and I can confidently say that he is an outstanding professional and an exceptional colleague. Konstantin combines deep technical expertise with an impressive ability to solve complex problems quickly and efficiently. What sets him apart is not only his knowledge, but also his positive attitude, reliability, and willingness to help others. He consistently earned respect and trust from everyone around him – both managers and teammates – because of his professionalism and strong work ethic. Whenever a challenging task appeared, Konstantin was the one people relied on to handle it with confidence and precision. His proactive mindset, clear communication, and ability to see the bigger picture made him a key contributor to our success. On top of that, he is a genuinely great person to work with – approachable, collaborative, and always bringing positive energy to the team. I can wholeheartedly recommend Konstantin as a top-level expert and an invaluable team player. Any company would be lucky to have him. ”
Aug 26, 2025— Pavlo Vynohradov“I had the pleasure of working closely with Kostiantyn on the AiQ project at RBC, where he served as the lead frontend developer. From the very beginning, it was clear that Kostiantyn brought not only a deep technical expertise, but also a genuine passion for building thoughtful, user-centric solutions. Our collaboration between frontend and backend was seamless — a rare and valuable alignment that made even the most complex tasks feel smooth and efficient. Kostiantyn consistently demonstrated initiative and creativity in solving architectural challenges, often proactively suggesting improvements that benefitted the entire system. He has an exceptional ability to think holistically, ensuring that the frontend architecture was not only elegant but also scalable and easy to integrate with backend services. His attention to detail, combined with a pragmatic mindset, made him a key contributor to the overall success of the platform. Beyond his technical skills, Kostiantyn is simply great to work with — reliable, communicative, and collaborative. Working with him felt like a true partnership, and I would welcome the opportunity to collaborate again on any future project.”
Jul 31, 2025— Jeff Qi
Colleague18 yrs exp“I had a great experience working with Konstantin. One thing I wanted to notice is that he is a professional in the frontend area, good problem solver and a very hard-working person. He knows how to prioritize tasks to make all the things work together in time.”
Nov 17, 2021— Ivan Kvitka“We worked with Konstantin on similar projects at Litslink. During this time, he has established himself as a proactive developer, rapidly growing, taking responsibility, and leading progress independently (in the Front End part). He had grown significantly as a software engineer within a year, and I hope to meet him on the same project again.”
Nov 17, 2021— Maksym Sviechnikov“I got a chance to work with Konstantin at Avatria. Konstantin helped me a lot when I joined the frontend team. He is smart and humble person with great attitude. He is very knowledgeable in React and ecosystem around React. He is an active participant and always comes up with unique ideas to solve a problem. As a former team member, Konstantin earns my highest recommendation. He would be an asset to any team in a frontend role.”
Nov 13, 2021— Kalpesh Patel
Colleague8 yrs exp“Konstantin was very useful while helping to build out v2 of Avatria Convert's web interface in React and TypeScript. A quick learner and diligent worker, he was able to adapt to new design patterns and move quickly. I would definitely recommend Konstantin for a future front-end role.”
Jun 10, 2021— Frank Fineis
Director11 yrs exp“I know Konstantin as an ambitious person with a high degree of responsibility and good knowlenge skills in frontend. All those qualities were noticeable to me during our participation in projects and competitions both on the same and different teams when we were worked at the Arnit company. His experience and qualities give him a competitive advantage in the labor market, especially in the field of frontend develop.”
Sep 14, 2020— Andrew Makalish
Colleague10 yrs exp“Konstantin is a frontend developer with great level of responsibility. He always wants to do the hardest feature you have. Also he has good personal characteristics.”
Dec 17, 2019— Dmytro Honcharov
Colleague11 yrs exp
