Mile Zajkovski, Developer in Düsseldorf, North Rhine-Westphalia, Germany
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Mile Zajkovski

Verified Expert  in Engineering

Back-end Developer

Düsseldorf, North Rhine-Westphalia, Germany
Toptal Member Since
November 13, 2019

Mile is an insightful software engineer, solutions architect, and developer lead, with over 15 years of experience. He works primarily on back-end challenges using tools from the Java ecosystem. He's passionate about cloud-native applications, big data, and real-time data processing applications.


Java, Spring, Amazon Web Services (AWS), SQL
Java 11, Spring Boot, Spring, Reactor, PostgreSQL, CircleCI, Docker...
Amazon Web Services (AWS), Amazon S3 (AWS S3), AWS Lambda, Amazon DynamoDB...




Preferred Environment

Jira, Git, IntelliJ IDEA, Eclipse, Linux

The most amazing...

...project I've worked on is a scalable back-end application supporting five million daily active users with real-time communication.

Work Experience

Java Developer (Property Management Systems)

2021 - 2022
  • Developed an integration with a third-party property management system, pooling data at regular time intervals and merging with local data.
  • Developed two new microservices using the Spring framework, one for managing properties and one for the automation of user access. Deployed on ECS using Terraform.
  • Developed parts of a back-office system used by support staff to help clients.
Technologies: Java, Spring, Amazon Web Services (AWS), SQL

Senior Backend Engineer

2021 - 2021
  • Developed a Java Spring Reactive client that imports e-books from a remote location (FTP) into AWS S3 and sequentially publishes them to Adobe Content Server.
  • Built a transformer for books metadata that transforms the data from Onix 2.1 format to Onix 3.0.
  • Created a Java Spring-based back-end job process for importing Onix books metadata from book providers into a centralized database.
Technologies: Java 11, Spring Boot, Spring, Reactor, PostgreSQL, CircleCI, Docker, Elasticsearch, Amazon S3 (AWS S3), Large-scale Computing, Relational Databases, Swagger

Senior Developer | Architect

2019 - 2021
  • Developed a back-end API that supports a social network for publishing and consuming multimedia content, using Node.js, AWS Lambda, DynamoDB, API Gateway, and AWS Cognito.
  • Developed a chat service for real-time messaging between users within the social app Narrate. The services support multimedia messages, paging, archiving message history into DynamoDB and later in S3, and push notifications for new messages.
  • Made a payment support API using Stripe, supporting one-time payments and subscriptions.
Technologies: Amazon Web Services (AWS), Amazon S3 (AWS S3), AWS Lambda, Amazon DynamoDB, Amazon API Gateway, Amazon Cognito, Serverless Framework, Serverless Architecture, Elasticsearch, Node.js, JavaScript, Asana, GitHub

Senior Architect

2019 - 2019
  • Led a team of three developers (one back end and two front end) in developing an eCommerce web application.
  • Developed microservices using Node.js, for matching of export and import companies based on their product offerings.
  • Deployed the services on AWS Lambda function, accessible as REST via AWS API Gateway.
  • Used AWS Cognito Service for user management, authentication, and authorization.
  • Developed the website using React. It enables authenticated users to browse and buy commercial information.
Technologies: React, Node.js, Amazon Web Services (AWS), AWS Lambda, Amazon Cognito, Amazon API Gateway, Serverless Framework, Relational Databases, TypeScript

Senior Engineer | Architect

2018 - 2019
  • Developed an image duplicates recognition service using perceptual hashes.
  • Developed a user/role management system with real-time synchronization with LDAP server and U2F functionality.
  • Developed single-sign-on functionality for multiple information systems, supported by two-factor authentication via SMS or a USB U2F token device.
Technologies: Spring MVC, MySQL, LDAP, PrimeFaces, Spring Boot, PostgreSQL, Relational Databases

Senior Software Architect

2017 - 2018
Flash Invite
  • Architected and developed the back end for a small social network app using AWS Lambda, Spring Cloud, Spring Data, and DynamoDB.
  • Developed a pilot version of a social networking app in React Native.
  • Automated the delivery process using AWS Code Pipeline, which we built and deployed, and AWS Elastic Beanstalk.
Technologies: Spring MVC, Spring Cloud, Spring Boot, React Native, Amazon Web Services (AWS), MongoDB Atlas, GitHub

Lead Software Engineer

2015 - 2018
Singular Group
  • Developed a system for the real-time processing of sports betting odds, their categorization, merging, and data enrichment using Spring, Artemis, and Hazelcast.
  • Developed a system for enabling tournament mode play of different casino games.
  • Developed a system for the configuration and execution of bonus awarding operations for casinos and sports betting players.
  • Developed a back-end system for slot machines, able to support over 3,000 spin rounds per second using medium-sized hardware.
Technologies: Spring MVC, Spring, WildFly, Apache ActiveMQ Artemis, Hazelcast, Java EE, Amazon Web Services (AWS), PostgreSQL, Data Structures, Large-scale Computing, Relational Databases

Lead Software Development Engineer

2013 - 2015
  • Developed an AI solution that scrutinized the behavior of soccer players.
  • Developed the first Unity-based version of Top Eleven - the number one mobile social soccer management game (over five million daily active users).
  • Developed the first iterations of a 3D game using Unity.
Technologies: Spring MVC, Spring, Java, Unity, PostgreSQL, Data Structures, Large-scale Computing, Relational Databases

Division Manager

2012 - 2013
Seavus Group
  • Led the technical sales teams into successfully completing multiple project sales, followed by project initiations.
  • Supervised and coached project managers on the subjects of development and testing.
  • Created and maintained the division projects portfolio.
Technologies: Hybrid Frameworks, iOS, Android

Technology Line Officer

2010 - 2012
Seavus Group
  • Managed the technology departments (Java, .NET, C++, Embedded) through their Line Managers.
  • Participated in the creation of the technology vision and strategy of the company.
  • Created and executed yearly technology development plans, which included tooling and training.
  • Monitored the technical sales process, which included technical solutions verification and estimations approvals.
Technologies: Java, .NET

Lead Software Engineer

2008 - 2009
Seavus Group
  • Developed an eCommerce web site for a language learning service.
  • Developed an automated test tool for testing firmware updates on mobile devices.
  • Developed a prototype for a news aggregation portal.
Technologies: Spring, Eclipse RCP, Java EE

Software Engineer and Product Manager

2006 - 2008
  • Developed an ERP product for the Dutch construction marker.
  • Developed reusable web components using Prototype.js.
  • Participated in requirements gathering and the composition of user stories.
Technologies: Microsoft SQL Server, JavaScript, Windows Communication Foundation (WCF), ASP.NET

Software Engineer

2006 - 2006
Seavus Group
  • Developed a web portal for presenting the multimedia content of musicians.
  • Developed a service for sending SMS push notifications.
  • Developed a service for the detection of suspicious payments.
Technologies: Integration, WebLogic, Java EE

Software Engineer

2003 - 2006
  • Developed an ERP system using Java and JSF.
  • Developed client-server application for the Ministry of Ecology used for collecting and analyzing weather conditions data.
  • Developed firmware for bar-code scanners with an on-device user interface and search functionality.
Technologies: Java, SQL, C, Delphi, .NET

Singular's Tournament System

Designed and implemented excellent scalability and the real-time processing of data in the Singular Tournament System. This enabled over 16000 match start signals to be sent to the clients on time (in less than two seconds). This was done with distributed processing using a JMS service, as well as a thorough optimization of the code, the environment, and the OS.

Singular's Slots-machines Services

Performed an extensive optimization of the code in the Slot-machines services, enabling them to support more than 3000 spin rounds per second on medium-sized hardware. Each round includes authorization, withdraw and deposit transactions, randomized outcome generation, and database persistence.

Top Eleven - Be a Football Manager
Implemented AI based on Behavior Trees for the "mind" of soccer players in a 2D simulation of a soccer game. The module was developed for the leading mobile social soccer manager game.

Image Duplicates Search

Implemented image duplicates search using the technique of perceptual hashes. The algorithm was able to successfully identify if two images are the same with 96% accuracy, even of resized or color-modified images.

Narrate - Monetize your fan base

A social networking app very similar to Patreon, where users can publish and purchase content and chat with each other.

We developed the app with a Node.js, AWS Lambda, DynamoDB back end, and a React Native mobile app.
1999 - 2013

Bachelor's Degree in Computer Science

Ss. Cyril and Methodius University of Skopje - Skopje, Macedonia

MAY 2019 - MAY 2022

AWS Solutions Architect Associate

Amazon Web Services


TOEFL English Language Certificate

Educational Testing Service

APRIL 2015 - APRIL 2017

Certified Scrum Master

Scrum Alliance


REST APIs, Node.js, Stripe, Stripe API, RESTEasy, JMS, JPA 2, React, Reactor


Eclipse IDE, IntelliJ IDEA, Amazon Simple Notification Service (Amazon SNS), Amazon Simple Queue Service (SQS), Apache Maven, Amazon Cognito, Lerna, Slack, MongoDB Atlas, Asana, GitHub, Git, Jira, Eclipse RCP, Apache ActiveMQ Artemis, WildFly, Amazon CloudWatch, AWS IAM, Amazon ElastiCache, CircleCI, Kafka Streams


Spring, Spring Boot, Spring MVC, Serverless Framework, Spring Security, JUnit, Hibernate, Swagger, .NET, ASP.NET, PrimeFaces, Unity, React Native


Java, HTML, JavaScript, SQL, C#, Delphi, CSS, C, Java 11, TypeScript


Serverless Architecture, Microservices, REST, Unit Testing


Relational Databases, Amazon S3 (AWS S3), Hazelcast, MySQL, SQL Server 2012, PostgreSQL, Amazon DynamoDB, Spring Data MongoDB, Spring Data JPA, Microsoft SQL Server, Elasticsearch, MongoDB, Redis


Java EE, AWS Lambda, Amazon EC2, Apache Kafka, Amazon Web Services (AWS), Linux, Eclipse, Android, iOS, AWS Elastic Beanstalk, Docker


Back-end, APIs, Back-end Development, Data Structures, Casinos & Gaming, Stripe Payments, Scalability, Scalable Architecture, Amazon API Gateway, EJB 3, Integration Testing, Fintech, Gaming, WebLogic, Integration, Windows Communication Foundation (WCF), Hybrid Frameworks, LDAP, Spring Cloud, Large-scale Computing

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