Dusan is available for hire

Dusan Simonovic

Verified Expert in Engineering

Software Developer

Belgrade, Serbia

Toptal member since February 8, 2017

Expertise

MySQL SQL Spring Java JUnit AWS MongoDB Agile Development Apache Kafka Spring Boot Microservices Development Docker OAuth Redis

Bio

Dusan is a full-stack Java and React developer with 15 years of software development experience. He's worked on several large projects, including Price2Spy, a tool for data web scraping for tracking competitor pricing on online shops, a social marketing tool for Adobe Marketing Cloud, an in-flight connectivity tool for a leading airline connectivity provider, and API integrations for a SaaS analytics provider.

Portfolio

Gartner

React, Java, Full-stack, Spring Boot

Secure Staffing LLC

Angular, React, Java

Patagonia Insurance, LLC

Spring, Java, React, Spring Boot

Experience

Java - 15 years
Spring - 15 years
Amazon Web Services (AWS) - 12 years
Apache Kafka - 9 years
REST - 9 years
Spring Boot - 9 years
Docker - 7 years
Microservices - 7 years

Preferred Environment

Apache Maven, Gradle, Windows, MacOS, Git, IntelliJ IDEA

The most amazing...

...project I've worked on is a huge social network marketing platform for Adobe Marketing Cloud.

Work Experience

Full-stack Java/React Developer

2022 - 2025

Gartner

Worked on developing a Google Chrome extension to display Google search results along with the results from the Gartner website for the logged-in user.
Operated on Gartner home page as a back-end developer, managing multiple core microservices.
Worked on developing and maintaining multiple AWS Lambda functions for various background processes.
Developed and managed infrastructure as a code (Terraform) module for the backing infrastructure for the microservices and Lambda functions I owned.

Technologies: React, Java, Full-stack, Spring Boot

Front-end Angular and React Developer

2020 - 2022

Secure Staffing LLC

Was a part of the development team working on a high-load website as a full-stack developer.
Used Asana to track work items and bugs and collaborate with the team.
Worked on a product for live video streaming with very high traffic.

Technologies: Angular, React, Java

Senior Full-stack Developer

2019 - 2019

Patagonia Insurance, LLC

Built a React-based front-end app from existing designs.
Built a Java/Spring back end for our web platform.
Implemented a full CI/CD pipeline using GitHub CI.
Set up AWS infrastructure for front end, back end, email sending, and more.
Integrated our web platform with various 3rd-party APIs (e.g., TrustedForm, LeadID, Google Tag Manager, Google Analytics, or Maxminds).

Technologies: Spring, Java, React, Spring Boot

Senior Full-stack Developer

2018 - 2019

U Group (former Bytecubed) (via Toptal)

Architected the Kafka backbone that is being used for event-based messaging between multiple microservices.
Made key contributions to module integration architecture through the Kafka backbone.
Developed back-end features in Java Spring and front ends in Angular and React.

Technologies: Angular, React, Apache Kafka, Java, Spring, Spring Boot

Senior Java Engineer

2018 - 2018

Datasnap, Inc. (via Toptal)

Implemented a data processing pipeline for processing trading events from a NASDAQ trading platform.
Achieved a very high throughput/low latency data processor. 10GB of data (360 million trading events) is processed (data transformation, aggregation, joins) in less than 20 minutes. End-to-end latency at the end of the project was below 1 millisecond.
Implemented a pluggable model to support different input reading and output format implementations.
Maintained full integration testing in a Docker container.
Built a full CI/CD pipeline to deploy the code to AWS with no downtime.

Technologies: Continuous Deployment, Continuous Integration (CI), Apache Kafka, Java, Spring Boot, Stock Price Analysis, High-load, Data Processing, Time Series Data

Senior Java Developer

2017 - 2018

MetaSaas (via Toptal)

Worked on integrations with various SaaS vendors using mostly REST.
Reviewed code and handled approvals for other developers.
Mentored and helped new developers start with integrations.
Developed an expenses matching mechanism using Expensify API and Elasticsearch.
Helped create integration testing for new integrations.

Technologies: MyBatis, Elasticsearch, OAuth, JSON Web Tokens (JWT), REST, Java, SaaS Operations (SaaSOps), Spring Boot

Senior Java Developer

2017 - 2018

Gogo, LLC

Led the development of a back-end tool used by airlines to track usage of the GogoAir in-flight entertainment system in real time.
Developed microservices (Spring REST services—Spring Cloud, Netflix OSS, AWS).
Built a deployment process (Netflix OSS, AWS, Spring Cloud).
Refactored some of the legacy code and migrated data from a data center to the cloud.
Enhanced security in an existing system by introducing asymmetric private/public key JWT token authentication.

Technologies: Amazon Web Services (AWS), Spring Cloud, Java, Spring Boot, Netflix OSS, Apache Kafka, React, JavaScript, Amazon DynamoDB, MySQL

Senior Java Engineer/Scrum Master

2015 - 2017

Endava d.o.o.

Led the remote element of a technical team in San Jose (USA), Belgrade (Serbia), and Noida (India).
Developed core services for the Adobe social media marketing platform.
Built a link shortening service to be used across the platform.
Created a label management service for managing content tags/labels.
Developed an asset service to store user assets to Amazon S3.
Presented at "Pass it on" sessions to help other members of the company to gain knowledge.

Technologies: Agile, Scrum, Git, MySQL, HBase, JDBI, Jersey, REST, Dropwizard, Java, Spring Boot, Social APIs

Web Developer and System Administrator

2010 - 2015

Webcentric d.o.o.

Contributed to the development of a tool for monitoring competitor prices on online shops.
Handled the deployment lifecycle of the application.
Maintained all application environments from development to production.
Architected a huge MariaDB Galera cluster with multiple nodes.
Mentored juniors and worked on developing them as professionals.
Set up and maintained a CI environment for deploying a custom Java application to a large set of remote VPS servers with no downtime.
Developed full-stack features (Java back-end, HTML/CSS/JS on UI).

Technologies: JPPF, Subversion (SVN), Spring, MariaDB, MyBatis, Java, Spring Boot, JavaScript

Experience

Price2Spy

http://www.price2spy.com

A tool used by web shop owners to monitor their competitors. By using this tool, they get notified about all the changes that happen on their competitors' shops, so they can react accordingly with price or any other adjustments.

Adobe Social - Core Services

https://www.youtube.com/watch?v=eIoGqPqKAv8

This tool is a huge set of modules that helps enterprise clients set up and maintain their social media marketing campaigns. This project was developed for a world-leading IT company, and its clients are some of the world's top companies.

MetaSaas Platform

MetaSaas is the best SaaS management tool for medium and large businesses. Manage SaaS vendors, reduce SaaS spend, and manage cloud applications from a single and easy-to-use dashboard.

As part of the MetaSaas team, my role was to develop more complicated integrations with SaaS vendors and to review and quality-check code for other developers. This involved using REST, OAuth, JWT, and more.

Gogo, Ltd.

https://www.gogoair.com/

Gogo is a leading in-flight connectivity and entertainment provider. As a member of the development team in Belgrade, I was involved in back-end and front-end development of the cloud solution for Airlines to track usage of the system in airplanes. This involved back-end development (Spring cloud, Netflix OSS) and UI (React and Redux).

Datasnap JTrain

A high-volume/low-latency data processing tool that processes events from the NASDAQ trading platform and produces output. This tool involved data lookup (joins), aggregation, and data transformation.

EinsteinMedicare

A web platform used to connect insurance buyers with insurance companies. It presents a multi-step form to a customer, which generates a lead that is sent to insurance companies. The back end is Java/Spring, and the front end is React, with full Gitlab CI/CD pipelines for auto deployments with zero downtime, all on the AWS infrastructure.

Publication

Get Started With Microservices: A Dropwizard Tutorial

https://www.toptal.com/developers/java/dropwizard-tutorial-microservices

Education

2009 - 2009

Cisco Certified Network Associate in Computer Networking

Cisco Net Academy - FTN Rao, Novi Sad Serbia

2000 - 2006

Master's Degree in Microcomputer Electronics

Faculty of Technical Sciences - Novi Sad

Certifications

DECEMBER 2022 - DECEMBER 2025

AWS Certified Solutions Architect — Associate

Amazon Web Services

Skills

Libraries/APIs

React, Apache Lucene, JDBI, MyBatis, Social APIs

Tools

RabbitMQ, Apache Solr, IntelliJ IDEA, Git, Gradle, Apache Maven, Subversion (SVN), GitLab CI/CD

Languages

SQL, Java, TypeScript, JavaScript

Frameworks

Spring, OAuth 2, Dropwizard, JUnit, Angular, Spring Boot, Jersey, JSON Web Tokens (JWT)

Paradigms

Reactive Programming, Microservices, Back-end Architecture, Continuous Delivery (CD), Scrum, Test-driven Development (TDD), Continuous Integration (CI), REST, Agile, Continuous Deployment

Platforms

Amazon Web Services (AWS), Docker, Apache Kafka, MacOS, Ubuntu, Windows, Linux

Storage

MongoDB, Amazon DynamoDB, Microsoft SQL Server, H2, Redis, MySQL, MariaDB, Elasticsearch, HBase, Cassandra, Databases

Other

Netflix OSS, Networks, JPPF, Spring Cloud, OAuth, SaaS Operations (SaaSOps), Full-stack, Galera Cluster, Scrum Master, Cloud Computing, Leadership, Multithreading, High-load, Data Processing, Time Series Data, Stock Price Analysis

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