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Rafael Kolloch

Senior Android Developer / Team-Lead

Rafael Kolloch
Dortmund, Germany

Experience

Feb 2021 - Apr 2025
4 years 3 months

Senior Android Developer / Team-Lead

IBM Deutschland

  • Further development and release support of a white-label e-prescription component for health insurance companies
  • Technologies: Android (Kotlin), Kotlin Multiplatform, Coroutines, Jetpack Compose, MVVM, StateFlow, Gradle, ProGuard
Jul 2020 - Dec 2020
6 months

Android Developer

ZGS Bildungs-GmbH (Deutsche Schülerhilfe)

  • Concept, architecture, development and deployment of the new online tutoring app for Deutsche Schülerhilfe
  • Technologies: Android (Kotlin), AndroidX, Android Jetpack, MVVM, LiveData, Room (SQLite), Retrofit, Gson, Firebase, push notifications, Zendesk, Gradle, ProGuard
Apr 2020 - Present
6 years

Full-stack Developer

Selbstständig

  • Development and maintenance of the research platform for stock investors "Trader Radar"
  • Technologies: Android (Kotlin), AndroidX, Android Jetpack, MVVM, LiveData, Room (SQLite), Retrofit, Gson, Firebase (Cloud Messaging, Crashlytics, Remote Config), in-app purchases, AdMob, Gradle, ProGuard, PHP, MySQL, HTML, CSS, JavaScript
Jan 2019 - Mar 2020
1 year 3 months

Lead Developer

Deutsche Bank

  • Lead development of a prototype and the subsequent design, deployment, and ongoing enhancement of a mobile payment app
  • Accompanying security audits and hardening
  • Technologies: Android (Kotlin), AndroidX, Android Jetpack, Room (SQLite+SQLCipher), Retrofit, Gson, Bluetooth, NFC, native communication with card terminals, encrypted databases and communication, Gradle, ProGuard, JUnit, Robolectric, Mockito, MockK
Jan 2019 - Dec 2019
1 year

Lead Developer

Leading German construction machinery provider

  • Lead development of a trade fair companion app
  • Technologies: Android (Java/Kotlin), AndroidX, Android Jetpack, Swagger CodeGen, encrypted databases and communication, Gradle, ProGuard, JUnit, Robolectric, Mockito, MockK
Jan 2017 - Present
9 years 3 months

Full-stack Developer

Self-Employed

  • Full-stack development of the math games app "Crystal Math"
  • Technologies: Android (Java), Google Standard Frameworks, SQLite, Retrofit, Firebase (Cloud Messaging, Real Time Database, Remote Config, Crashlytics), Facebook SDK, Gradle, ProGuard, PHP, MySQL
Jan 2017 - Dec 2019
3 years

Lead Developer

Leading German logistics company

  • Designing, deploying and continuously improving a comprehensive mobile app
  • Performing security audits and hardening
  • Technologies: Android (Java), Google Standard Frameworks, Dagger2, SQLite, Retrofit, Swagger CodeGen, database and communication encryption, Gradle, ProGuard
Jan 2017 - Dec 2017
1 year

Android Developer

Leading German automotive supplier

  • Development of a companion app for light e-mobility vehicles
  • Technologies: Android (Java), Bluetooth LE, database and communication encryption
Jan 2015 - Dec 2016
2 years

Android Developer

Swiss Bank

  • Development of a mobile banking app in close collaboration with the client's team
  • Technologies: Android (Java), Android-JavaScript bridge, communication encryption

Industries Experience

See where this freelancer has spent most of their professional time. Longer bars indicate deeper hands-on experience, while shorter ones reflect targeted or project-based work.

Experienced in Education (9 years), Banking and Finance (9 years), Information Technology (9 years), Healthcare (4 years), Insurance (4 years), and Transportation (3 years).

Education
Banking and Finance
Information Technology
Healthcare
Insurance
Transportation

Business Areas Experience

The graph below provides a cumulative view of the freelancer's experience across multiple business areas, calculated from completed and active engagements. It highlights the areas where the freelancer has most frequently contributed to planning, execution, and delivery of business outcomes.

Experienced in Information Technology (11 years) and Product Development (11 years).

Information Technology
Product Development

Skills

  • Activity Areas: Architecture, Consulting, Development, Feasibility Analysis
  • Programming Languages: Kotlin, Java, Objective-c, Swift, Php
  • Ides: Android Studio, Intellij Idea, Xcode, Eclipse, Netbeans, Visual Studio Code
  • Industries: Automotive, Banking, Logistics, Lottery, Public Sector, Retail, Utilities, Insurance
  • Android: Android Sdk, Kotlin Multiplatform, Jetpack Compose, Koin, Dagger2, Coroutines, Mvvm, Mvp, Mvi, Room, Livedata, Sqlite, Sqlcipher, Retrofit, Okhttp, Gson, Firebase (Ads, Cloud Messaging, Crashlytics, Realtime Database, Remote Config), Admob, Glide, Picasso, Timber, Material Design Ui, Biometric Authentication (Fingerprint), Gradle, Unit Tests, Junit, Mockito, Mockk, Robolectric, Release Management
  • Ios: Afnetworking, Cocoapods, Cocoalumberjack, Firebase (Ads, Crashlytics, Cloud Messaging), Release Management
  • Misc: Regular Expressions, Reverse Engineering, Pentesting, Web Scraping
  • Project Management / Ci: Scrum, Atlassian Toolchain, Jira Administration/customization, Bitbucket, Jenkins, Teamcity, Sonarqube
  • Databases: Sqlite (With Sqlcipher), Mysql, Oracle, Db2, Postgresql
  • Platforms: Windows, Linux/unix, Macos
  • General It Skills: Common Office Suites Like Ms Office And Open Office, Experience With Graphics Editing Tools Like Photoshop, Gimp

Languages

German
Native
English
Advanced
Polish
Advanced
Spanish
Elementary

Education

Oct 2004 - Jun 2010

TU Dortmund

Diploma · Computer Science · Dortmund, Germany

Oct 2001 - Jun 2004

FernUniversität in Hagen

Part-time distance learning · Computer Science · Hagen, Germany

Aug 2001 - Jul 2004

Training as an IT Specialist (Application Development)

Vocational Training · IT Specialist (Application Development) · Dortmund, Germany

...and 1 more

Profile

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Frequently asked questions

Do you have questions? Here you can find further information.

Where is Rafael based?

Rafael is based in Dortmund, Germany and can operate in on-site, hybrid, and remote work models.

What languages does Rafael speak?

Rafael speaks the following languages: German (Native), English (Advanced), Polish (Advanced), Spanish (Elementary).

How many years of experience does Rafael have?

Rafael has at least 11 years of experience. During this time, Rafael has worked in at least 4 different roles and for 9 different companies. The average length of individual experience is 1 year and 3 months. Note that Rafael may not have shared all experience and actually has more experience.

What roles would Rafael be best suited for?

Based on recent experience, Rafael would be well-suited for roles such as: Senior Android Developer / Team-Lead, Android Developer, Full-stack Developer.

What is Rafael's latest experience?

Rafael's most recent position is Senior Android Developer / Team-Lead at IBM Deutschland.

What companies has Rafael worked for in recent years?

In recent years, Rafael has worked for IBM Deutschland, Selbstständig, and Self-Employed.

Which industries is Rafael most experienced in?

Rafael is most experienced in industries like Education, Information Technology (IT), and Banking and Finance. Rafael also has some experience in Healthcare, Insurance, and Transportation and Logistics.

Which business areas is Rafael most experienced in?

Rafael is most experienced in business areas like Information Technology (IT) and Product Development.

Which industries has Rafael worked in recently?

Rafael has recently worked in industries like Education, Information Technology (IT), and Banking and Finance.

Which business areas has Rafael worked in recently?

Rafael has recently worked in business areas like Information Technology (IT) and Product Development.

What is Rafael's education?

Rafael holds a Master in Computer Science from TU Dortmund.

What is the availability of Rafael?

Rafael is immediately available full-time for suitable projects.

What is the rate of Rafael?

Rafael's rate depends on the specific project requirements. Please use the Meet button on the profile to schedule a meeting and discuss the details.

How to hire Rafael?

To hire Rafael, click the Meet button on the profile to request a meeting and discuss your project needs.

Average rates for similar positions

Rates are based on recent contracts and do not include FRATCH margin.

1200
900
600
300
Market avg: 980-1140 €
The rates shown represent the typical market range for freelancers in this position based on recent contracts on our platform.
Actual rates may vary depending on seniority level, experience, skill specialization, project complexity, and engagement length.