Antonio Zemunik, Developer in Zagreb, Croatia
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Antonio Zemunik

Verified Expert  in Engineering

Full-stack JavaScript Developer

Zagreb, Croatia
Toptal Member Since
April 13, 2020

Antonio is a full-stack JavaScript developer who enjoys learning new things and polishing projects to perfection. He built his experience initially through e-learning, working with leading clients in the domain, and afterward working for one of the biggest Dutch banks. Antonio's expertise reaches end-to-end features development, project leadership, communication with designers, clients, and managers, overseeing the development, and ensuring efficient and well-structured code.


JavaScript, TypeScript, Node.js, React, NestJS, Amazon Web Services (AWS)...
Extension Engine
Jest, Mocha, Heroku, POI, Webpack, React, Vue, MongoDB, PostgreSQL, MySQL...
Ericsson Nikola Tesla
SoapUI, GlassFish, Apache Maven, Java




Preferred Environment

React, Vue, Express.js, Node.js, Amazon Web Services (AWS), Microsoft Azure, NestJS, GraphQL, NoSQL, SQL

The most amazing...

...project I've worked on is an EPUB (e-book) format reader with various user options. Today, it is being used on Harvard by its students and professors.

Work Experience

Senior Full-stack JavaScript Developer

2020 - PRESENT
  • Worked on a bank's chatbot platform with a rich technology stack and multiple teams. The platform supports two chatbots, one appearing on the official webpages of ABN AMRO Bank and the other one for internal employees in Microsoft Teams.
  • Achieved big success with the chatbot (90% of successful answers, both in English and in Dutch), which IBM wrote about.
  • Worked on internal projects used for automating processes between the teams, such as delivering chatbot conversations data to the analytics teams and tools, building a platform for chatbot configurations, etc.
  • Worked on the transition of microservices and applications, maintained by my team, from AWS to Azure and Kubernetes architecture.
  • Oversaw application development, mentored junior team members, included in planning and research of projects, discussions with business analysts, product owners, technical leads of peer teams, etc.
  • Involved in application perspective, infrastructure decisions, and writing logic underneath CI/CD pipelines.
Technologies: JavaScript, TypeScript, Node.js, React, NestJS, Amazon Web Services (AWS), Microsoft Azure, Jenkins, CI/CD Pipelines, Bitbucket, GraphQL, Hasura, XState, Apollo, Botkit, Microsoft Teams, Splunk, CSS, Less, Sass, HTML, REST, Redis, Bootstrap, REST APIs, Redux, Architecture, Microservices, Amazon DynamoDB, Serverless, Full-stack, Next.js, Chatbots

Senior Full-stack JavaScript Developer

2015 - 2020
Extension Engine
  • Collaborated with leading clients in that field, such as Harvard Business Publishing, New Teacher Center, Laureate Network, CGMA, etc., on several projects within the e-learning domain.
  • Remained in constant communication with clients' side, designers team, QA team, and other developers.
  • Contributed to a teaching improvement platform used among many USA universities, an EPUB reader used in Harvard classes among students and teachers, a medical data tool presented in The White House, etc.
  • Implemented features on the back-end application side, set up the REST architecture, and worked with SQL and NoSQL database types.
  • Implemented features on the front-end application side and worked on HTML, CSS, and JavaScript code parts. Constructed the front-end application skeleton and set up bundling configuration.
  • Oversaw application development, participated in the code review process, and mentored younger developers. I ensured that the code was written cleanly and efficiently and that, among code quality, the team had good development velocity.
Technologies: Jest, Mocha, Heroku, POI, Webpack, React, Vue, MongoDB, PostgreSQL, MySQL, Express.js, Node.js, CSS, Less, Sass, GitLab, HTML, Chartist.js, TestCafe, REST, Redis, Bootstrap, REST APIs, Redux, Architecture, Microservices, Amazon DynamoDB, Serverless, Full-stack, Next.js, Chatbots, EPUB

Java Developer Intern

2014 - 2014
Ericsson Nikola Tesla
  • Contributed to a platform that communicates with sensors and calculates gas consumption in a household as a Java intern developer.
  • Won the 3rd prize for the best student project in that academic year at the University of Zagreb, Croatia.
  • Worked in Java, my primary language at the time when I was a student.
Technologies: SoapUI, GlassFish, Apache Maven, Java

Bot Studio

A tool built for automating processes between the internal teams in ABN AMRO Bank. The software enables easier collaboration between the teams and speeds up the processes. It comprises three main parts: chatbot configuration, FSM workflows for deploying data science data, and Label Studio implementation for existing user chats.

I was the technical lead on this project, making decisions with the product owner and planning sprints and quarters with the business analyst. I laid down the foundation of the architecture and later led a team of nine people.

Chatbots Anna and Abby
Two virtual assistants that use IBM Watson underneath. Anna is an external-facing agent for retail and commercial banking customers, appearing on all official web pages of ABN AMRO Bank. Abby is an internal agent available through the bank's portals and Microsoft Teams to support its teams and employees.

Anna has more than one million conversations annually, resolving 90% of customers' requests, both in Dutch and in English.


I was a software development team member and worked as a back-end engineer on this project. Around 100 people were behind building these chatbot platforms, separated into several teams, such as the machine learning team, content creators, UI designers, software engineers, etc.

New Teacher Center

A platform that improves teaching systems among many universities in the USA. New Teacher Center is a nonprofit organization dedicated to improving student learning by guiding a new generation of educators. Most universities agreed, using NTC, to use this platform to strategically enhance their teaching system and raise the quality of their work, so from 2020, the platform is being used across the USA.

I worked on this project from the beginning, collaborating in the research and development phases. I was one of the two leading developers on a team of seven developers.

The platform also uses our in-house built content authoring platform, named Tailor:

Language Buddies

Slack bot for matching students and helping them overcome language barriers. It was built for Laureate International Universities that enroll students from various parts of the world.

I worked as a lead developer and was directly involved in research and development decisions, planning bot features, and estimating development time.

Chartered Global Management Accountant (CGMA)

A learning management system for one of the leading companies in the field of online learning, especially in the games and VFX industry.

I worked as a full-stack developer within a team of six developers.

The project also used our in-house built content authoring platform, named Tailor:

Harvard Business Publishing

EPUB (e-book) format reader built from scratch that contains various options (e.g., text annotations, color blindness assistance, playing videos and interactives, working in offline mode, etc.). The project is now being used daily during classes at Harvard among its students and professors.

Foundation Medicine

Diagram representation of medical data related to various diseases. The project was made for a medical organization in the USA, and the solution was presented at the medical encounter in The White House, Washington, DC.

I worked entirely independently during the development time, so I collaborated with the product owner and project manager in the application design and planning.

Machine to Machine (mCommerce)

A platform that communicates with sensors and notifies users about monthly gas expenses. I contributed as a Java intern developer to this project. I won the 3rd prize for the best student project in that academic year at the University of Zagreb, Croatia.
2013 - 2015

Master's Degree in Information and Communication Technology

Faculty of Electrical Engineering and Computing, University of Zagreb - Zagreb, Croatia

2010 - 2013

Bachelor's Degree in Computing

Faculty of Electrical Engineering and Computing, University of Zagreb - Zagreb, Croatia


Magna Cum Laude

Faculty of Electrical Engineering and Computing, University of Zagreb


First Certificate in English (FCE)

Cambridge English


Node.js, Vue, Vuex, REST APIs, React, jQuery, D3.js, Slack API, Google Sheets API, Backbone.js, Marionette.js, Chartist.js


Webpack, Sequelize, Mongoose, Git, GitHub, Jenkins, Microsoft Teams, Mocha, Botkit, CircleCI, Bitbucket, GitLab, Apache Maven, SoapUI, Gulp, Splunk, Doccano


Express.js, Vuetify, Nuxt.js, Bulma, Jest, NestJS, Redux, Next.js, Bootstrap, Selenium, TestCafe


CSS, HTML, Less, Sass, JavaScript, TypeScript, GraphQL, SQL, Java


REST, Microservices


PostgreSQL, MySQL, MongoDB, Hasura, NoSQL, Amazon DynamoDB, Redis


Amazon Web Services (AWS), Heroku, Kubernetes, Kaltura, Meteor, Docker


POI, CI/CD Pipelines, Apollo, Architecture, Serverless, Full-stack, Chatbots, Microsoft Azure, XState, GlassFish, AmCharts, EPUB

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