Stefan is available for hire
Hire StefanStefan Kostic
Verified Expert in Engineering
Full-stack Developer
Vranje, Serbia
Toptal member since February 17, 2021
Bio
Stefan is a software engineer with a focus on full-stack web development. He has also worked on blockchain-related projects. Stefan's passions are high-quality software and good software practices. He tries to ensure he is not limited to only web development or one specific role—he enjoys variety and learning new skills. Stefan has experience working on enterprise projects, in startup environments, and as freelancer.
Portfolio
Shamir Labs
Go, Ethereum
END-Labs
Amazon Web Services (AWS), JavaScript, Solidity, Ethereum, Node.js, Next.js...
Unibright
Blockchain, Tendermint, Cosmos, Go, Docker, Vue, Solidity, React, Node.js...
Experience
Availability
Part-time
Preferred Environment
Visual Studio Code (VS Code), Git, Windows, OS X, Linux
The most amazing...
...project I've collaborated on was a mainnet for Baseledger, the blockchain for baselining.
Work Experience
Senior Go Engineer
2023 - PRESENT
Shamir Labs
- Contributed to the development of a non-custodial Ethereum liquid staking protocol powered by distributed validator technology (DVT).
- Integrated the protocol with Ethereum execution clients.
- Collaborated on the integration with Ethereum consensus clients.
Technologies: Go, Ethereum
Blockchain Software Engineer
2022 - PRESENT
END-Labs
- Implemented and designed smart contracts for the DeFi protocol.
- Worked on the Implementation of various AWS Lambda microservices.
- Implemented the full-stack application for the DeFi protocol.
Technologies: Amazon Web Services (AWS), JavaScript, Solidity, Ethereum, Node.js, Next.js, Blockchain, Decentralized Finance (DeFi), Back-end, Full-stack, REST, REST APIs, Back-end Development, Full-stack Development, APIs, Front-end, Amazon S3 (AWS S3), Jira, Cloud Storage, GitHub, AWS IAM, Amazon RDS, Serverless Framework, AWS Amplify, Document Processing, Leadership, HTML5, Ghost, Fintech, Figma, User Interface (UI), UI Development, Bitbucket, CI/CD Pipelines, Smart Contracts, API Integration, Web Hosting, MongoDB, Automation, Go
Software Engineer
2021 - PRESENT
Unibright
- Developed the mainnet for the Baseledger blockchain used for baselining.
- Contributed to the Baseledger smart contract for splitting payments.
- Worked on the testnet for the Baseledger blockchain used for baselining.
- Implemented various MVP solutions to implement the baseline protocol using Baseledger.
- Implemented an app for NFT minting with a successful public mint on Ethereum.
Technologies: Blockchain, Tendermint, Cosmos, Go, Docker, Vue, Solidity, React, Node.js, PostgreSQL, Back-end, Full-stack, REST, REST APIs, Back-end Development, Full-stack Development, APIs, CSS, Front-end, Jira, Cloud Storage, GitHub, Redux, C#, ASP.NET, Leadership, HTML5, .NET Core, Fintech, User Interface (UI), UI Development, SCSS, Bitbucket, CI/CD Pipelines, Smart Contracts, API Integration, Rust, Web Hosting, MongoDB, Automation, Google Cloud Platform (GCP)
Baseline Core Developer and Maintainer, Member of TSC
2021 - PRESENT
Freelance
- Served as a member of the Technical Steering Committee for 2022/2023.
- Participated actively as an open-source contributor to the Baseline Protocol as a core developer and maintainer.
- Implemented various parts of the Battleship game with zero-knowledge proofs, Kafka messaging communication, and other baseline components.
- Implemented an Excel file showcasing the Baseline Protocol using the Baseledger blockchain.
- Led the development of a Hello, World! app for baselining the Battleship game.
- Participated in reference implementation of Baseline Protocol.
Technologies: Node.js, Docker, Apache Kafka, zkSNARKs, Ganache CLI, NestJS, Full-stack, REST, REST APIs, Back-end Development, Full-stack Development, APIs, Front-end, Distributed Systems, GitHub, C#, ASP.NET, Leadership, .NET Core, User Interface (UI), UI Development, SCSS, Bitbucket, CI/CD Pipelines, Smart Contracts, API Integration, Automation, PostgreSQL, Next.js, Google Cloud Platform (GCP)
Software Engineer
2016 - PRESENT
Freelance
- Integrated a blockchain framework, the first of its kind, and their customers with Baseline protocol, connecting traditional systems via Ethereum Mainnet.
- Worked on a security token platform for a blockchain company.
- Maintained and implemented new features for students' work management system.
Technologies: Angular, JavaScript, .NET, Blockchain, Azure, Docker, Back-end, Full-stack, REST, REST APIs, Back-end Development, Full-stack Development, APIs, MySQL, Front-end, GitHub, Redux, Python, C#, ASP.NET, HTML5, .NET Core, User Interface (UI), UI Development, SCSS, Bitbucket, CI/CD Pipelines, Smart Contracts, API Integration, Nuxt.js, Web Hosting, MongoDB, Automation, PostgreSQL, Next.js, Google Cloud Platform (GCP), Go
Founding Blockchain Engineer
2023 - 2023
Omni Network
- Participated in all design and development phases of Cosmos SDK protocol to enable cross-rollups communication between Ethereum L2 rollups.
- Set up infrastructure for two testnets with millions of transactions and hundreds of thousands of users.
- Contributed to the creation of various blockchain tooling, including a faucet, with millions of transactions.
Technologies: Go, Solidity, Cosmos, Google Cloud Platform (GCP), Bash Script, JavaScript, Ethereum
Software Engineer
2021 - 2021
Provide
- Participated in the development of the Provide Payments application.
- Contributed to the development of the Provide stack that consists of multiple Go services.
- Contributed to the development of the Provide Shuttle application.
Technologies: Go, Vue, Docker, Blockchain, Back-end, Full-stack, REST, REST APIs, Back-end Development, Full-stack Development, APIs, Front-end, Cloud Storage, Redux, C#, ASP.NET, HTML5, .NET Core, User Interface (UI), UI Development, Bitbucket, CI/CD Pipelines, API Integration, Automation, Next.js
Software Engineer
2019 - 2021
WorkSpan
- Enhanced and added new features to the WorkSpan web application.
- Rewrote legacy module for tasks management and rewrote ag-grid to use server-side row model, implementing many custom features not supported by ag-grid.
- Migrated Webpack from version 3 to version 4 in a complex hybrid Angular application.
- Fixed bugs and supported the WorkSpan web application.
- Participated in the migration from AngularJS to Angular and rewrote legacy code from CoffeeScript to TypeScript.
- Improved the process for code reviews with automatic test execution on Jenkins.
Technologies: AngularJS, Angular, JavaScript, CoffeeScript, Webpack, Angular Material, HTML, TypeScript, Full-stack, REST, REST APIs, Back-end Development, Full-stack Development, APIs, Front-end, Jira, Redux, Python, HTML5, Figma, User Interface (UI), UI Development, SCSS, Bitbucket, CI/CD Pipelines, Google Cloud, API Integration, Automation
Software Engineer
2016 - 2019
Zühlke Engineering AG
- Served as a full-stack engineer on a large distributed enterprise project for FIFA events, together with IBM.
- Implemented a low-code blockchain integration framework for enterprise use, with visual process modeling tools, code generation, and process monitoring as a core team member of the first blockchain project at the company.
- Contributed to an open-source project that enables the calculation of the energy consumed by personal blockchain transactions.
- Built a web platform for digital services such as analytics and process automation as an IoT project for a company that offers underground installation and trenchless renewal of pipelines.
- Acted as a member of focus groups, including a blockchain focus group. Helped organize meetups—most notably an international blockchain meetup in Belgrade.
Technologies: .NET, AngularJS, Angular, Blockchain, Aurelia, Azure, Back-end, Full-stack, REST, REST APIs, Back-end Development, Full-stack Development, APIs, MySQL, Front-end, Jira, C#, ASP.NET, HTML5, .NET Core, Business Rules Engine, User Interface (UI), UI Development, SCSS, Bitbucket, CI/CD Pipelines, API Integration, Automation
Experience
Baseledger Developer
https://baseledger.net/I am currently working on the mainnet for the Baseledger blockchain used for baselining. Previously I worked on a testnet for Baseledger blockchain used for baselining (named Lakewood) that is working without downtime with over a million blocks.
I implemented various MVP solutions to illustrate the Baseline Protocol, and as a Baseledger developer, I am also contributing to the Baseline Protocol.
I implemented various MVP solutions to illustrate the Baseline Protocol, and as a Baseledger developer, I am also contributing to the Baseline Protocol.
WorkSpan
Supported and maintained the application and added new features as a front-end developer.
In addition, I migrated webpack, implemented server-side tables, and improved some of the engineering processes.
In addition, I migrated webpack, implemented server-side tables, and improved some of the engineering processes.
Integration with Baseline Protocol
Integration of a blockchain low-code framework for business integrations with baseline protocol, an open-source initiative aimed at synchronizing private business processes, like document exchange, via a public blockchain.
Blockchain Low-code Platform for Business Integration
Served as a core member of developing the back-end for a unified blockchain-based business integration platform. Worked on an automatic Ethereum smart contract generation from a UI-template, automated deployment, and interaction with a smart contract through various smart adapters. I also participated in setting up the infrastructure on Azure.
Project for Calculating Estimation of Blockchain CO2 Emission
The Carbonara Coinpensator (carbonara.info) is a blockchain-related open-source project established by Unibright and Zuehlke Engineering. The main goal of the project is to raise awareness about the energy consumption of public blockchains. I contributed to the research and served as a back-end developer.
IoT Project for a No-dig Equipment Company
Worked on a web platform to help users make optimum use of their equipment. The web platform offers services in areas such as data analytics and process automation. As a result, customers can now use their no-dig equipment more efficiently, and it gives the company more insight into adapting products and services to customer needs.
Education
2014 - 2017
Master's Degree in Computer Science
University of Belgrade, Faculty of Mathematics - Belgrade, Serbia
2011 - 2014
Bachelor's Degree in Computer Science
University of Belgrade, Faculty of Mathematics - Belgrade, Serbia
Certifications
SEPTEMBER 2017 - PRESENT
Professional Scrum Developer I (PSD I)
Scrum.org
Skills
Libraries/APIs
Vue, Node.js, React, REST APIs, AWS Amplify
Tools
Bitbucket, Git, Jira, Webpack, Docker Compose, Ganache CLI, GitHub, AWS IAM, Ghost, Figma
Languages
JavaScript, TypeScript, Solidity, HTML, Go, C#, HTML5, SQL, Python, SCSS, CoffeeScript, Rust, CSS, Bash Script
Frameworks
.NET, Angular, Next.js, Redux, ASP.NET, AngularJS, NestJS, Serverless Framework, .NET Core, Business Rules Engine, Aurelia, Angular Material, Tendermint, Nuxt.js
Paradigms
Automation, REST, Unit Testing, Scrum, Agile
Platforms
Azure, Google Cloud Platform (GCP), Blockchain, Amazon Web Services (AWS), Visual Studio Code (VS Code), Windows, OS X, Docker, Ethereum, Apache Kafka, Linux
Storage
PostgreSQL, MySQL, Amazon S3 (AWS S3), Google Cloud, MongoDB
Other
Front-end, Back-end, Leadership, UI Development, CI/CD Pipelines, Smart Contracts, API Integration, Software Development, Software Design, Data Structures, Full-stack, Back-end Development, Full-stack Development, APIs, Distributed Systems, Document Processing, Fintech, User Interface (UI), Mathematics, Research, Writing & Editing, Bitcoin, Open Source, Cosmos, Solana, Non-fungible Tokens (NFT), zkSNARKs, Decentralized Finance (DeFi), Cloud Storage, Amazon RDS, Web Hosting
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