Kadir Celep

Kadir Celep

Software Engineer in Berlin, he/him


I join teams to deliver mobile experiences by coding, coaching, leading.



Side Projects


I started to fix things and design solutions to tiny struggles of daily life using 3D printing.
Started as a hobby during the global pandemic but my design for coffee filter holders was loved and bought by more than 200 coffee snobs from all around the world.



Bootstrapped a mobile application for iOS and Android using Flutter to help curious adults to efficiently level up their knowledge by accessing the content curated by experts on topics that matter. Qwoll was funded and supported by HTW Berlin.

Work Experience

2021 — Now
Freelance Software Engineer at LabTwin, Gorillas, Visa Cybersource, BeyondBuild

Since 2021, I've collaborated with a diverse range of clients, from startups to established companies.

LabTwin is an AI voice assistant for medical labs. The Android app suffered from regressing bugs and concurrency issues. I created a refactoring plan (without stopping the feature development). I reduced code complexity, optimized RxJava and Coroutines usage and improved overall testability. I also introduced the team to Jetpack Compose and coroutines which reduced the lead time. (2022-2023, Berlin).

At the peak of their growth, Gorillas needed a large team to deliver their new Android app. I implemented the post order experience by following an MVI architecture using Jetpack Compose and standard Kotlin libraries. I also co-created a tracking library for interacting with multiple services by all development teams independently. (2022, Berlin).

Processing nearly a trillion dollars every year, reliability for their payment SDK was a top priority for Cybersource by Visa. I enhanced CI/CD configurations (Jenkins), migrated Gradle scripts to Kotlin, and brought dependencies to their latest stable versions as well as Kotlin. (2021-2022, Berlin & Munich)

BeyondBuild needed a tenant app for Bauwens’ newly built smart apartments in Berlin. The Android app required multiple account management, custom UI elements for IoT devices, push notifications and messaging. I delivered the app in 4 months using Jetpack Compose and Kotlin coroutines following an MVI structure. I also set up CI on Github Actions, internal and beta distribution on Firebase and SDK integrations for marketing, IoT SDK and Jitsi SDK. (2021, Berlin)

2019 — 2021
  • Managed & led 2 cross functional teams for the mobile apps of lastminute.com group
  • Conducted 1:1s, guided personal development goals, managed hiring.
  • Encouraged and maintained short feedback loops, communication and visibility of work within teams and organisation.
  • Planned features and technical tasks. Juggled the trade-offs of complexity and risks.
2017 — 2019

Qixxit was acquired by lastminute.com

Led a cross functional team of mobile, web and backend engineers to relaunch Qixxit (a multimodal train+bus+flight booking app founded by Deutsche Bahn in late 2016).

Planned features. Investigated and estimated complexity.

Initiated and developed the Qixxit Android application from scratch. Created the architectural design with a reactive state management.

Contributed to the higher level engineering architecture and the product roadmap.

Participated in the hiring process by conducting cultural fit interviews.

2015 — 2017

Bonial, part of Axel Springer SE, is a leading drive to store marketing partner across Europe. I worked on the architectural design, development and maintenance processes of retail applications for Android.


2010 — Now

The Community Volunteers Foundation undertakes projects #intheNameofYouthPower to create social peace and open up spaces where youth can learn from each other.