Nikola is available for hire

Nikola Stanojevic

Verified Expert in Engineering

Back-end Developer

Belgrade, Serbia

Toptal member since April 25, 2018

Expertise

Back-end Developers Payment Processing SQL Spring Boot Java PostgreSQL AJAX Full-stack MySQL PHP CSS Linux Swagger JUnit Git

Bio

Nikola is a talented engineer specializing in full-stack software development. Before moving into consulting, he spent six years working in the mobile communications industry, where he designed and implemented scalable, high concurrency software solutions. Nikola is a supportive and enthusiastic team player dedicated to streamlining processes and efficiently resolving project issues and is willing to take ownership of core components.

Portfolio

Old Dominion Transportation Group

Java, Spring Boot, Android, PostgreSQL, MySQL, Amazon Web Services (AWS)...

SwissRe iptiQ - Main

Spring Boot, Java, Apache Kafka, PostgreSQL, MongoDB, AWS IoT, Event Sourcing...

Virtual Assets LLC

Spring Boot, React, MySQL, Git, Java, SOAP, Asana, Payment APIs...

Experience

Java - 10 years
Back-end - 10 years
Spring Boot - 10 years
MySQL - 9 years
PostgreSQL - 8 years
PHP - 8 years
Payment Gateways - 4 years
React - 2 years

Availability

Part-time

Preferred Environment

Git, Linux, IntelliJ IDEA, Jira

The most amazing...

...thing I've done in my career was to work with a team on creating an MVNO (mobile virtual network operator) from scratch over a period of two years.

Work Experience

Software Consultant and Team Manager

2019 - PRESENT

Old Dominion Transportation Group

Managed a team of three developers to design and deliver a taxi service vehicle tracking system for insurance reporting purposes, used by over ten fleets in two countries.
Led a team of three developers, a designer, and a QA on building a Taxi service SMS and credit card payment solution used by more than ten fleets in the United States.
Developed an Android application for credit card processing via Stripe's BBPOS Chipper 2X BT solution.

Technologies: Java, Spring Boot, Android, PostgreSQL, MySQL, Amazon Web Services (AWS), iCabbi, Payment APIs, Payment Processing, Swagger, SQL, Gradle, JUnit, Integration Testing, Unit Testing, Liquibase

Java Engineer

2021 - 2024

SwissRe iptiQ - Main

Developed a technical accounting microservice using CQRS to keep accounting records for insurance sales.
Helped multiple teams transition microservices from CRUD to CQRS approach with great success.
Identified and resolved key issues with microservices such as bank payments, accounting, and underwriting.

Technologies: Spring Boot, Java, Apache Kafka, PostgreSQL, MongoDB, AWS IoT, Event Sourcing, CQRS, Kibana, Grafana, Message Queues, Swagger, OpenAPI, SQL, JUnit, CI/CD Pipelines, Flyway, Integration Testing, Unit Testing, Kubernetes

Full-stack Developer

2019 - 2021

Virtual Assets LLC

Built a website that allowed users to trade cryptocurrency by depositing cash in one of the 11,000 participating retailers or via ACH (automated clearing house) and converting them to Bitcoin, Ethereum, or Litecoin.
Integrated with Green Dot's "At The Register" SOAP-based API to facilitate cash deposits.
Implemented Sila's ACH payment API to allow users to deposit their funds directly from their bank accounts.
Implemented Block.io and BitGo APIs to support cryptocurrency transfer between different wallets.

Technologies: Spring Boot, React, MySQL, Git, Java, SOAP, Asana, Payment APIs, Payment Processing, JavaScript, Java Servlets, SQL, Integration Testing, Unit Testing

Java Developer

2018 - 2019

Fast Rope Labs

Developed a near real-time bridge between a custom CRM system and two external CRM platforms: Microsoft Dynamics 365 and Salesforce.
Combined the Salesforce API and SOQL to support data synchronization between the Salesforce platform and the custom CRM system.
Integrated the Dynamics 365 REST API to support synchronization of data between the Microsoft Dynamics 365 platform and the custom CRM system.
Optimized Play Framework by creating a plugin to support executing jobs on multiple, user-defined queues to prevent system congestion caused by long-running tasks.
Speeded up queue processing by 50% per thread by implementing modern concurrency patterns.

Technologies: Back-end, Amazon Web Services (AWS), REST, Redis, PostgreSQL, Python, Play, Java, Java Servlets, SQL

Back-end Developer

2017 - 2018

Pihinga Ltd

Designed and implemented the entire back-end stack for the company's influence marketing platform. This consisted of database design, building RESTful API interfaces, logging, and testing.
Implemented the PayPal API to the platform to provide subscription payments for members.
Integrated the platform with AWS to provide an advanced user experience when adding and removing offers.
Integrated the platform with the most popular social networks, including Facebook, YouTube, Instagram, Pinterest, and others.
Set up and implemented system scheduling and maintenance processes which helped to make the platform faster and more space-efficient.
Established testing and production environments, including automated testing and deployment.

Technologies: Back-end, Cron, cPanel, Apache, MySQL, PHP, SQL

Java Developer

2011 - 2017

Procescom

Designed and developed multiple core modules such as instant messaging, real-time billing, rating, promotion, and customer care for Globaltel MVNO (mobile virtual network operator) over a period of two years.
Developed SMS Gateway: a scalable, failure-resistant, high-concurrency system for routing SMS messages via SMPP and HTTP (Kannel) protocols across many content providers and networks.
Built PromoBox platform—a platform that allows mobile operators to manage and offer special promotions to their customers.
Designed and developed kvib.me universal messaging system—a universal chatting platform via web and USSD (unstructured supplementary service data).
Led a team on the implementation and development of a USSD gateway and USSD menu browser for BH Telecom.

Technologies: Tcpdump, Linux, SOAP, Back-end, Git, REST, SLF4J, PostgreSQL, Spring Boot, Java, Java Servlets, SQL

Experience

InstaVesti App

I designed and developed the InstaVesti website and Android app, a news aggregation application for the Serbian language. The application uses natural language processing (NLP) to detect similar news articles and combine them to avoid repetition while also using this technology to automatically group news articles into categories.

Globaltel MVNO

https://www.globaltel.rs/

I designed and developed multiple core modules such as instant messaging, real-time billing, rating, promotion, and customer care for Globaltel MVNO (mobile virtual network operator) over a period of two years.

Crypto Dispensers

https://cryptodispensers.com/

I designed and developed a cryptocurrency trading platform that enabled users to deposit funds to their accounts via cash deposits at one of the 11,000 participating retailers or via ACH Bank deposits, and later convert them to a cryptocurrency of their choice such as Bitcoin, Ethereum, or Litecoin.

Education

2005 - 2009

Bachelor's Degree in Computer Engineering

RAF (Racunarski Fakultet) - Belgrade, Serbia

Skills

Libraries/APIs

Stripe, PayPal API, OpenAPI, Java Servlets, SLF4J, React, jQuery, Apache Lucene, Facebook API, Liquibase

Tools

Tcpdump, Git, Gradle, Flyway, Apache, Cron, IntelliJ IDEA, Jira, Asana, ActiveMQ, Kibana, Grafana

Languages

Java, SQL, PHP, HTML, CSS, Python, JavaScript

Frameworks

Spring Boot, Play Framework, Swagger, JUnit, Play, Hibernate

Paradigms

Unit Testing, Agile Software Development, Concurrent Programming, REST, Object-oriented Programming (OOP), Event Sourcing, CQRS

Storage

PostgreSQL, MySQL, Redis, MongoDB

Platforms

Amazon Web Services (AWS), Linux, NetBeans, cPanel, Android, Apache Kafka, AWS IoT, Kubernetes

Other

Back-end, Payment APIs, Payment Processing, Integration Testing, iCabbi, Payment Gateways, SOAP, SMPP, Ajax, Full-stack, CI/CD Pipelines, Front-end, Computer Engineering, Message Queues

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