Rafael Kolloch - Senior Android Developer / Team-Lead

Q: Where is Rafael based?

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

Q: What languages does Rafael speak?

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

Q: 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.

Q: What is Rafael's latest experience?

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

Q: What companies has Rafael worked for in recent years?

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

Q: 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 .

Q: Which business areas is Rafael most experienced in?

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

Q: Which industries has Rafael worked in recently?

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

Q: Which business areas has Rafael worked in recently?

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

Recommended expert

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

Created

September 2025

Last Update

September 2025

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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.