Tomo Krajina, Developer in Poreč, Croatia
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Tomo Krajina

Verified Expert  in Engineering

SMPP Developer

Poreč, Croatia
Toptal Member Since
February 5, 2014

Tomo is a Java, Android, and Golang developer with 13+ years of experience. He has worked on Android, web, and back-end applications, telecommunications, and enterprise and banking systems. He is especially interested in all things GPS related.


Firebase, Amazon DynamoDB, AWS Lambda, PHP, Android, Google Cloud, Python, Java...
Fintech, Go
Android, iOS, Google Cloud Platform (GCP), Java, Go




Preferred Environment

Linux, Bash, Android Studio, IntelliJ IDEA, Git, Vim Text Editor

The most amazing...

...thing I've built is an open source library that is now used to track wild animals in Africa.

Work Experience


2015 - PRESENT
  • Worked and maintained various open source projects.
  • Mantained several websites and their internal microservices.
  • Developed an Android application for language learning to help users learn new words by going through 10,000 sentences.
  • Created an Android application for numeric sequences and time tracking.
  • Developed a news aggregation Android application complete with back-end.
  • Integrated Android apps with Firebase and Google cloud back-ends.
  • Maintained Trackprofiler, the online GPS track editor.
Technologies: Firebase, Amazon DynamoDB, AWS Lambda, PHP, Android, Google Cloud, Python, Java, Go

Back-end Engineer

2017 - 2017
  • Developed the back-end in Golang.
  • Implemented various fintech APIs.
Technologies: Fintech, Go

Back-end Engineer

2015 - 2016
  • Implemented a back-end REST API hosted on Google Cloud.
  • Implemented video processing workflow.
  • Implemented a variant HLS video streaming solution.
  • Helped the development of iOS and Android applications.
  • Integrated REST APIs with mobile apps.
  • Integrated push notifications with mobile apps.
Technologies: Android, iOS, Google Cloud Platform (GCP), Java, Go

Senior Java Developer

2010 - 2015
  • Developed enterprise SMS messaging systems.
  • Implemented various applications using the SMPP protocol.
  • Implemented the GSMA OneApi REST API.
  • Developed open-source client libraries for the OneAPI REST API.
  • Introduced the Git versioning system and worked on a specific Git workflow to be adopted.
  • Introduced Groovy scripting for several applications.
Technologies: Ruby, PHP, SMPP, Web Services, Apache Tomcat, Groovy, Python, Spring, Java

Senior Java Developer

2004 - 2010
Istarska kreditna banka (Istrian Credit Bank)
  • Implemented an internet banking back-end system.
  • Worked on several web applications for internal use.
  • Worked on an application for money laundering prevention.
  • Implemented a reporting system.
Technologies: AS400, Web Services, Apache Tomcat, Spring, Java

Lead Developer

2005 - 2009
Aqua d.o.o.
  • Implemented a bridge between an application for inventory management and the company's CMS (a WordPress plugin and a Java service).
  • Implemented a CMS and web shop.
Technologies: Java, PHP

Math and Informatics Teacher

2000 - 2004
Elementary School Poreč
  • Taught kids programming (mostly Python) and mathematics.
  • Mentored regional and state level competitions.
  • Lobbied for the use of open-source technologies in the educational system.
Technologies: Python

10,000 Sentences
10,000 sentences an Android app for language learning. It helps users learn new words in a foreign language. The idea is to go through 10,000 sentences in a target language. By exposing users to unknown words in a real context (a sentence) they learn new words.

Gpxpy is a Python library for GPS/GPX tracks. It implements all the most common algorithms used to manipulate and analyze GPS track data.

A statical analysis tool to discover long and complex functions in Golang. The user decides which measures of complexity to use, for example: number of variables in scope, number of assignments, nested blocks, cyclomatic complexity, ceomplexity per line of code, etc.

Typescriptify Golang Structs
A helper tool and library to seamlessly use Golang models in Typescript.

Trackprofiler is an online GPS track editor intended for hikers, mountain bikers, and outdoor lovers. Users can upload their tracks, fix common GPS errors, split or join tracks, add elevation data, etc. Tracks can be uploaded via email or from Dropbox.

Git Introduction: Uvod u git

An introductory book about Git in Croatian.

GraphAnything is an Android application to help users visualize various number sequences. For example: tracking weight, running distance and speed, or time spent on a project. It can also be used as a pomodoro timer.

Golang reflection simplified.

Ftmpl is a fast, compiled, and typesafe templating language for Golang.

Geo Elevations:
A Python library for the Shuttle Radar Mission Data (SRTM) and the Earth Gravitational Model (EGM2008).
1993 - 1999

Bachelor's of Science Degree in Math

PMF - Zagreb


Google Maps, Leaflet, jQuery, JasperReports, jQuery UI


Firebase Cloud Messaging (FCM), Android Studio, IntelliJ IDEA, Vim Text Editor, LaTeX, Shell, Apache Tomcat, Git


Go, Python, Java, Groovy, Bash, PHP, Ruby


Agile Software Development, Test-driven Development (TDD)


Android, Google App Engine, Firebase, Linux, Google Cloud Platform (GCP), iOS, AWS Lambda, Heroku


Google Cloud, MySQL, Amazon S3 (AWS S3), Amazon DynamoDB, Memcached, IBM Db2, Microsoft SQL Server


Spring, Apache Struts 2, webapp2, React Native


SMS, SMPP, Web Services, AS400, Fintech

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