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Sasa Macakanja

Verified Expert in Engineering

Software Developer

Zagreb, Croatia

Toptal member since July 14, 2014

Expertise

Front End Full-stack Back-end Developers API Prompt Engineering REST API JavaScript HTML5 SQL AWS Redis PostgreSQL

Bio

Sasa is a proven software engineer with 15+ years of professional experience developing complex web applications and production-ready online platforms. He specializes in server and client-side programming with React on the front end and Node.js on the back end. Sasa is an avid believer in Agile web development and Kanban workflow.

Portfolio

Meridian Studio

Agile Software Development, Redis, Express.js, PostgreSQL, WebStorm...

Construction Management SaaS Platform

TypeScript, Python, React, Next.js, Fastify, Redis, PostgreSQL, RAG Pipelines...

Nettbil

JavaScript, Node.js, React, REST APIs, Amazon Web Services (AWS), Amazon EC2...

Experience

Redis - 10 years
PostgreSQL - 10 years
Node.js - 8 years
React - 8 years
TypeScript - 8 years
Amazon EKS - 5 years
Python - 2 years
Go - 1 year

Preferred Environment

Linux, Git, Vim Text Editor, WebStorm, MacOS

The most amazing...

...system I've built for the last six years as a lead engineer is a fast and modern real-time car auction web platform using modern web technologies in the cloud.

Work Experience

Founder & Lead Software Architect

2014 - PRESENT

Meridian Studio

Founded a computer software agency that builds custom IT solutions for other companies, mostly startups and scale-ups.
Handled project management for agile software development projects.
Offered consultations for choosing proper tech stacks, infrastructure in the cloud, and modern web technologies.
Built modern web applications that scale and run in production without bottlenecks for business operations.

Technologies: Agile Software Development, Redis, Express.js, PostgreSQL, WebStorm, Amazon S3 (AWS S3), Test-driven Development (TDD), APIs, Background Jobs, Webpack, Databases, Amazon EKS, Software QA, Software Architecture, Front-end, Full-stack, RESTFul APIs, SQL, Data Analysis, Artificial Intelligence (AI), Architecture, Component Libraries, REST, MongoDB, Terraform, Infrastructure as Code (IaC), Docker, Clean Architecture, Security, Data Modeling, Amazon Simple Queue Service (SQS), Prompt Engineering, Gemini, Third-party APIs, Relational Databases, Full-stack Development, Vercel, Claude Code

Principal Software Engineer

2025 - 2025

Construction Management SaaS Platform

Architected a scalable, cloud-native construction management platform together with founding engineers.
Engineered a high-performance front-end rendering for large-scale project management features (grids), reducing load times and enabling easy future scaling.
Redesigned core services using clean architecture principles to separate business logic from frameworks and infrastructure, reducing code dependency complexity and cutting average feature development time in the future with fewer breaking changes.
Implemented advanced real-time context-based chat communication for project management and scheduling.
Orchestrated the strategic migration to TypeScript alongside a transition to clean architecture, enforcing strict interface contracts that increased unit test coverage.
Architected a centralized, transient state store using Zustand to manage complex project data flows, ensuring <100ms UI latency during real-time updates of large blueprint datasets and grids.
Engineered a RAG-based AI system, automated the extraction and vectorization of unstructured construction documents to enable semantic search capabilities and chats.
Engineered a memory-safe PDF generation service using Node.js streams, enabling the export of large page construction reports without memory overflows and reducing server RAM usage.

Technologies: TypeScript, Python, React, Next.js, Fastify, Redis, PostgreSQL, RAG Pipelines, Chatbots, AWS IoT, Zustand, Application State Management, Web, Clean Architecture, Shadcn, Role-based Access Control (RBAC), Security, Back-end Development, Data Modeling, Radix UI, AI Integration, Prompt Engineering, Gemini, Third-party APIs, Relational Databases, Non-relational Databases, Agentic AI, Full-stack Development, Large Language Models (LLMs), Tailwind UI, AI Tools, Figma, Data Pipelines, Claude Code

Full-stack JavaScript Developer

2019 - 2025

Nettbil

Developed and continuously improved a complex web platform of many connected back-end and front-end applications for running fast and reliable real-time car auctions for end users.
Migrated the application architecture from a monolith application using domain-driven development to carefully chosen microservices.
Served as a lead engineer in the core tech team. Together with the CTO of the company, I scaled up the tech stack and tech team from a startup to a scaleup and later to a modern enterprise environment.
Ensured that the production environment runs smoothly for daily business operations using modern monitoring tools and ensured the stability of services.
Migrated the production environment to use a managed Kubernetes platform in the cloud.
Added a QA automated testing development environment before production deployment to ensure proper feedback to the developers and to catch any new feature bugs and possible regressions in different parts of the platform.
Maintained a complex infrastructure in the cloud as code and ensured regular backups were done according to company policies.
Participated in scaling the tech team with different types of engineering roles, ensured a smooth onboarding process, and mentored new hires.
Integrated the platform with machine learning services built for our features.

Technologies: JavaScript, Node.js, React, REST APIs, Amazon Web Services (AWS), Amazon EC2, Amazon S3 (AWS S3), MySQL, DevOps, Kubernetes, Go, Python, Machine Learning, Redis Pub/Sub, Redis Queue, Redis, Amazon ElastiCache, Background Jobs, Domain Modeling, Software QA, Software Architecture, Next.js, Agile Software Development, Amazon Elastic Container Registry (ECR), WebStorm, Test-driven Development (TDD), APIs, Amazon Elastic Container Service (ECS), Webpack, Databases, Amazon EKS, EventSource, Front-end, CI/CD Pipelines, Full-stack, RESTFul APIs, SQL, Data Analysis, Tailwind CSS, API Integration, Artificial Intelligence (AI), ETL, Architecture, CSS, HTML, Testing, Component Libraries, Cypress, Figma to React, REST, Microservices, System Design, Team Leadership, Microfrontends, Fastify, Terraform, Infrastructure as Code (IaC), Docker, BullMQ, Application State Management, Web, Clean Architecture, Role-based Access Control (RBAC), Security, Back-end Development, Data Modeling, Datadog, Events, Google Cloud Platform (GCP), AI Integration, Prompt Engineering, Gemini, Third-party APIs, Relational Databases, Non-relational Databases, Full-stack Development, Optical Character Recognition (OCR), Tailwind UI, Figma, Data Pipelines

Front-end Web Developer

2018 - 2019

Johnson & Johnson - Health IT

Implemented new features for a digital health coaching platform using Agile software development processes.
Helped deliver the new front-end application based on React with server-side rendering, CSS modules for styling, and Redux for state management and custom middleware.
Created responsive cross-browser CSS layouts as well as optimized page speed and web app performance.
Tested, debugged, and refactored a legacy JavaScript application with partial migration to React.
Developed code with TDD using Jest (unit testing, integration testing, some functional testing) and continuous deployment and delivery using Jenkins.
Implemented new features and changes for a back-end API proxy and increased code coverage with unit testing.
Handled SAML-based SSO authentication implementation.

Technologies: Express.js, Node.js, React, JavaScript, Java, PostgreSQL, WebStorm, Test-driven Development (TDD), APIs, Webpack, Responsive Web Design (RWD), Software QA, Front-end, RESTFul APIs, API Integration, CSS, HTML, Testing, Component Libraries, Web, User Interface (UI), HIPAA Compliance

Senior Software Engineer

2017 - 2018

Blacc Spot Media, Inc.

Contributed to the development of multiple complex web application projects with full-stack JavaScript.
Implemented advanced real-time communications features based on WebRTC to enable human communication via voice and video in a web browser.
Created several RESTful JSON APIs in Node.js frameworks with complete end-to-end testing.
Wrote front-end single-page applications in TypeScript using best practices for code organization (components, pages/containers, services, models, redux for state management).
Created pixel-perfect HTML/CSS templates according to the project design.
Completed the configuration of AWS infrastructure for several projects, including Amazon Elastic Container Service for easy deployment, management, and scaling of Docker containers running applications.
Implemented continuous deployment and delivery based on Travis and AWS infrastructure with custom bash scripts.
Set up a separate job queue service backed by Redis, built for Node.js.

Technologies: Amazon Web Services (AWS), Bash, React, Node.js, JavaScript, PostgreSQL, TypeScript, REST APIs, Redis, Stripe API, Redux, Amazon Elastic Container Registry (ECR), WebStorm, Amazon S3 (AWS S3), Test-driven Development (TDD), APIs, Background Jobs, Hapi.js, Amazon Elastic Container Service (ECS), Webpack, Responsive Web Design (RWD), Stripe Subscriptions, Databases, Software QA, Angular 2, Software Architecture, Front-end, Full-stack, RESTFul APIs, SQL, API Integration, CSS, HTML, Testing, Component Libraries, Angular, REST, BullMQ, Application State Management, Web, Role-based Access Control (RBAC), Security, Back-end Development, Data Modeling, Amazon Simple Queue Service (SQS), HIPAA Compliance, Stripe, Third-party APIs, Relational Databases, Non-relational Databases, Full-stack Development

Full-stack Web Developer

2013 - 2018

Subos

Set up the required architecture for a project called "Subos App" and built the system.
Implemented required functionalities, including a Laravel RESTful API back end and AngularJS front end.
Set up the build and deploy procedures for deploying to the hosting service.
Built a complex registration form for new members, including a complete admin CRUD interface with authentication, roles, groups, members' pages, PDF generation (ZendPDF), and automated email sending via Mandrill.
Made optimizations primarily targeting mobile platforms.

Technologies: AngularJS, Laravel, PostgreSQL, PHP, REST APIs, WebStorm, APIs, Background Jobs, Responsive Web Design (RWD), Databases, Angular 2, Front-end, Full-stack, RESTFul APIs, SQL, CSS, HTML, REST, Web, Role-based Access Control (RBAC), Security, Back-end Development, Relational Databases, Full-stack Development

Web Developer

2014 - 2016

Persice

Created two separate single-page web applications for desktop and mobile browsers using Angular.
Wrote both the front-end applications in TypeScript and shared the same common codebase (services, models, Redux stores) between them.
Implemented an advanced build system based on Webpack 2 with features for improved performance and speed in a production environment (Async loading of modules, Treeshaking, and AOT (ahead of time/offline) compilation).
Implemented continuous deployment and delivery based on Jenkins.
Created unit tests and end-to-end tests for the entire Angular codebase.
Built a chat and real-time notification service based on websockets (Socket.IO, Node.js, and Redis Pub/Sub).
Implemented JWT (JSON Web Token) authentication for RESTful API and Socket.IO WebSocket server built on Node.js Express framework.
Implemented a social networking login based on the Facebook OAUTH2 API, allowing users to log in and connect to other users on the platform.
Set up and maintained a separate production environment for serving front-end files: Nginx, Node.js, and Amazon S3 storage for static files and images.
Implemented a front-end feature to connect additional Twitter and LinkedIn social networking accounts.

Technologies: Redis, Socket.IO, Node.js, TypeScript, Webpack, PostgreSQL, Facebook API, Background Jobs, Responsive Web Design (RWD), Databases, Angular 2, SQL, CSS, HTML, Web, User Interface (UI), Role-based Access Control (RBAC)

Full-stack Web Developer

2014 - 2014

Bail Binder

Implemented required functionalities, including a Laravel RESTful API back end and AngularJS front end.
Implemented a single-page app built with AngularJS for the front end.
Set up the build and maintenance procedures for deploying to the cloud hosting service.
Integrated the SaaS with external API services, Mandrill and Mailchimp for email campaigns, and Stripe for billing.
Built and customized the landing page for the SaaS with WordPress CMS.

Technologies: Laravel, React, APIs, Background Jobs, Responsive Web Design (RWD), Databases, Angular 2, Full-stack, RESTFul APIs, SQL, CSS, HTML, Angular, REST, Web, Role-based Access Control (RBAC), Back-end Development, Data Modeling, Relational Databases, Full-stack Development

Web Developer

2014 - 2014

NDA

Joined the existing web development team working to improve and finish a project management web application.
Implemented performance improvements to the initial AngularJS concepts and components for their app.
Worked in a consulting and R&D role for choosing web technologies.
Implemented stress-testing on the real-time application.
Handled server administration for cloud hosting services.

Technologies: Trello, MySQL, AngularJS, Laravel, Express.js, PostgreSQL, APIs, Responsive Web Design (RWD), SQL, HTML, Web

Full-stack Web Developer

2008 - 2012

Edunet

Implemented a WordPress CMS platform for managing landing pages and signups for courses.
Built a complex web registration form for signing up for courses.
Implemented front-end and back-end customizations.
Implemented Moodle as a learning management system for the Cisco Networking Academy.
Implemented the front end using HTML5 and Less, and incorporated responsive web design techniques.

Technologies: Moodle, PHP, MySQL, jQuery, WordPress, Responsive Web Design (RWD), Full-stack, SQL, HTML, Web, Full-stack Development

Web Developer

2008 - 2009

Croatian Academic and Research Network

Joined the web development team to help with the official public launch of www.carnet.hr.
Improved the existing codebase, fixed various front-end and back-end bugs, and polished the UI for the launch.
Handled front-end implementation using HTML5, CSS3, and jQuery. Incorporated responsive web design techniques.
Implemented required back-end functionalities in a custom PHP framework.
Developed and set up a custom CMS for page and user access administration.

Technologies: CSS, HTML, JavaScript, MySQL, PHP, Responsive Web Design (RWD), Adobe Photoshop, SQL, Web, Relational Databases, Non-relational Databases

Experience

Nettbil

https://www.nettbil.no

An online car auction platform for selling cars from private individuals to car dealers in Norway. I joined Nettbil as a full-stack software engineer, improving and evolving the core auction platform in the back end and front end. I also worked to improve the infrastructure in Nettbil's cloud provider. I spearheaded the stability of daily business operations and the ever-increasing number of cars in auctions over the years. Later, I became a staff engineer and continued working there for six years, scaling the team and platform applications with the original founders from the startup phase to a more enterprise phase with new owners.

Corporate Web for Croatian Academic and Research Network - CARNet

As part of a big web development team, I contributed to rebranding and creating entirely new corporate web pages for the Croatian Academic and Research Network. I worked as a front-end and back-end software developer.

Persice

https://github.com/Persice/persice.com

A startup project for building a minimum viable product to validate an idea for a need to create a social networking application, which precisely connects you to people and events that match your mutual interests.

Fitness Membership Web Application

An AngularJS and Laravel web application for the student organization "Subos." The project was very challenging and interesting for me because it included building a very complex registration form for new members, a complete admin CRUD interface with authentication, roles, groups, a trainers' pages optimized for mobile access, members pages, PDF generation (ZendPDF), and automated sending of emails via Mandrill. The site uses Laravel 4 on the back end and AngularJS on the front end. I single-handedly developed the entire site from the ground up to production state, and supported it through the whole development lifecycle.

BailBinder

A software-as-a-service application for the bail bond industry. It was built as a full-stack web application with a separate back end and front end as a minimum viable product for an early startup phase and is ready to be validated for bail bond agencies.

Healthcare Platform for Real-time Audio/Video Consultations and Appointment Scheduling

A complete healthcare platform for the management and registration of users and hospitals/facilities.

Features:
• Live consultations between patients and doctors, with file sharing, chat, and video/audio real-time communications in the browser via WebRTC
• Automated events and notifications handling
• Automated and manual generation of PDF reports after consultation ends based on the doctor's report
• Integration with Stripe and Twilio

Education

2003 - 2008

Progress Toward a Bachelor's Degree in Telecommunications and Informatics

Faculty of Electrical Engineering and Computing - Zagreb, Croatia

Skills

Libraries/APIs

Stripe API, REST APIs, React, Node.js, Redis Queue, Facebook API, Stripe, jQuery, Socket.IO, PayPal API

Tools

WebStorm, Webpack, Moodle, Amazon EKS, Terraform, Amazon Simple Queue Service (SQS), Claude Code, Amazon Elastic Container Service (ECS), Amazon Elastic Container Registry (ECR), Adobe Photoshop, Shadcn, Figma, Vim Text Editor, Git, Trello, Celery, Amazon ElastiCache

Languages

Sass, TypeScript, JavaScript, HTML5, SQL, Less, PHP, Bash, Python, CSS3, HTML, CSS, Java, C, Go

Frameworks

Express.js, Hapi.js, Laravel, Redux, Next.js, Tailwind CSS, Cypress, Angular, Fastify, Angular 2, AngularJS, Django

Paradigms

Test-driven Development (TDD), Agile Software Development, Responsive Web Design (RWD), Redis Pub/Sub, Testing, REST, Microservices, Clean Architecture, Role-based Access Control (RBAC), DevOps, ETL, HIPAA Compliance, Microfrontends

Platforms

Amazon Web Services (AWS), Docker, Vercel, Google Cloud Platform (GCP), WordPress, MacOS, Linux, Amazon EC2, Kubernetes, Web, AWS IoT

Storage

Redis, Amazon S3 (AWS S3), PostgreSQL, Databases, Datadog, Relational Databases, Data Pipelines, MySQL, Memcached, MongoDB, Elasticsearch

Other

APIs, Background Jobs, Software Architecture, Web Technologies, Message Queues, EventSource, Front-end, CI/CD Pipelines, Full-stack, RESTFul APIs, UI Testing, API Integration, Architecture, Component Libraries, Figma to React, System Design, Team Leadership, Infrastructure as Code (IaC), BullMQ, Zustand, Application State Management, Security, Back-end Development, Data Modeling, Events, AI Integration, Prompt Engineering, Gemini, Third-party APIs, Full-stack Development, Tailwind UI, Stripe Subscriptions, User Interface (UI), Data Analysis, Artificial Intelligence (AI), Design Systems, Radix UI, Non-relational Databases, Agentic AI, Large Language Models (LLMs), Optical Character Recognition (OCR), AI Tools, Computer Networking, Algorithms, Machine Learning, Domain Modeling, Software QA, RAG Pipelines, Chatbots

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