Sasa Slavnic, Developer in Belgrade, Serbia

Sasa Slavnic

Java Developer

Belgrade, Serbia
Toptal Member Since
June 3, 2014

Software developer and architect with 10+ years of experience in software development. His main area of interest is mobile development. He enjoys working with startups and building products.

Sasa is available for hire
Hire Sasa


React, JavaScript, iOS, Swift, Android, Kotlin, Java
Grails, Groovy, PostgreSQL, iOS, Android, Java
PostgreSQL, Java


Belgrade, Serbia



Preferred Environment


The most amazing...

...thing I've coded is an app written in C# and DirectX that is similar to Google Earth but handles 1.4TB of satellite photos using no more than 200MB of memory.

Work Experience

2013 - PRESENT

Owner and Lead Developer

  • Developed an Android app for brain monitoring using custom-made hardware.
  • Developed an iOS app for finding nearby promotions and deals.
  • Developed an Android app for a food delivery back-office.
  • Developed Android and iOS app for limo booking (white labeled customer app, driver app and back-office app).
  • Developed Android and iOS client apps for sport betting.
  • Developed Android and iOS apps for beauty venues (customer app for booking, as well as a back-office app for venue employees).
  • Developed an Android and iOS app for the truck fleet management.
  • Developed an Android app for fashion brands (customer app, white labeled).
  • Developed an Android app for warehouse management.
Technologies: React, JavaScript, iOS, Swift, Android, Kotlin, Java
2009 - 2013

Chief Java Architect

  • Led the development of mobile products for a Swiss telecom, such as XtraZone, MyTone, and SwisscomTV.
  • Led and coached the team in mobile app development.
  • Reviewed software architecture, set coding standards, and conducted code reviews.
  • Made technology-related decisions on a company level.
  • Developed next-generation CRM software, including a Java back-end and JavaFX front-end.
Technologies: Grails, Groovy, PostgreSQL, iOS, Android, Java
2007 - 2009

Lead Developer
  • Created a back-end for Google ad tracking using Java.
  • Designed and implemented a high-availability stack based on open source technologies.
  • Created a Java app for Google AdWords campaign management and optimization.
  • Ensured smooth operations and zero downtime for the entire platform.
  • Led a small and focused team of developers, making sure that best development practices were always applied.
Technologies: PostgreSQL, Java
2004 - 2007

Chief Development Officer

  • Created a mobile solution for courier delivery management using .NET CF and a .NET back-end.
  • Developed a mobile messenger app as part of a fleet tracking and management solution. Used C++ and deployed on Windows CE platform.
  • Created several client applications in the area of computer telephony integration.
  • Maintained massive amounts of legacy C++ code.
  • Led a small development team, making sure to keep up-to-date with technologies and tools.
Technologies: Embedded C++, Microsoft SQL Server, C#, C++


PillarLearning | Codi
System design, architecture, and implementation for an IoT smart toy. Developed an IBM cloud-based Node.js back end (with some interesting Watson integrations), iOS, and Android companion apps. Designed messaging protocol between device, apps, and the back end.

Showcase Jobs
iOS application for conducting video interviews with job seekers.


Android app for monitoring brain waves coming from a specialized EEG device. The app fetched data from an EEG device via Bluetooth protocol in real time, and it does various scientific calculations and data transformations. The app is not publicly available; it is distributed together with the EEG device.

DavEl | BostonCoach

iOS app for booking and tracking limo rides.

Swisscom TV

Swisscom TV is an IPTV platform for Swiss telecom customers. Part of the platform are companion apps for mobile devices. My role was to build large portions of Android application (EPG grid, Video player, recording management...). In addition, I did consulting for iOS app and refactored a lot of inherited code on both platforms.

Limo Anywhere
iOS apps for black limo ride booking. This was a white label app that was customized and deployed over 500 times. Extensive use of fastlane and custom build scripts.

AdTraffic SEM Optimization Platform
Platform for real-time optimization of Google AdWord campaigns. The platform was able to create large campaigns based on a set of rules, set by small, custom developed DSL. Further, the platform tracked campaign performance in real time and adjusted the campaign on a daily basis for better performance. My role in the project was to build the back end and to handle high-availability requirements.

Swoffice Twentyone
Twentyone was supposed to be next-gen CRM software, with a rich client part written in JavaFX and a Java back end. My role in the project was to set up the entire system architecture and build the JavaFX application and parts of the back end.

Swisscom Xtra-zone

Swisscom xtra-zone was a messaging platform for Swiss telecom customers (now discontinued). As part of the platform, I developed the iOS app and later on helped in improving the Android app as well.


Sandwichboard (now discontiuned) was supposed to provide a simple way to find promotions near you. I made a prototype of the iOS application for the platform, which connected to a REST back end and displayed rich data (with different styles, backgrounds, and fonts).


I organized a hackathon for developing cool and innovative Google Glass apps. More than 30 developers contributed with seven great projects.

Tech Talk at MobCon BG

I gave a presentation on some useful lesser-used Android features.

Tech Talk at Java2days, Bulgaria
I gave a presentation about the specifics of Android tablet development.

Tech Talk at Codemotion, Italy
I gave a presentation about Java and Objective-C with some language comparisons aimed at helping Java developers dig into iOS development.

Tech Talk at Jazoon, Switzerland
I gave a presentation on JavaFX technology, sharing experiences from one of the first enterprise projects developed on this platform.


Booking app for beauty venues, iOS and Android.



Swift 5, Swift, Java, C#, JavaScript 6, C++, Embedded C++, JavaScript, Groovy, Python, Kotlin


Cocoa Touch, Android SDK, Grails


Adobe Photoshop, Firebase Cloud Messaging (FCM), Asana, Android Studio, Xcode, Trello, SourceTree, Crashlytics


Agile Software Development, Scrum, Kanban, Rapid Application Development (RAD), REST, Rapid Prototyping, Unit Testing, Design Patterns


iOS, Android, Firebase


PostgreSQL, Microsoft SQL Server


System Architecture, Software Engineering, Google, Back-end Development, WebSockets, APNs, IBM Watson Speech-to-Text, Software Architecture, Native Mobile Apps, IBM Cloud


DoubleClick API, CocoaPods, Node.js, Firebase iOS SDK, Firebase Android SDK, React, React Redux, Google API, Google Maps SDK


2005 - 2009

Master's Degree in Information Technology

Technical Faculty M. Pupin - Zrenjanin, Serbia

2000 - 2003

Bachelor's Degree in New Computer Technologies

VETS - Belgrade, Serbia