Lead JavaScript Developer
2019 - PRESENT24me- Maintained the Node.js back end.
- Planned a new API structure.
- Migrated old code to a modern runtime.
- Made deployments to an AWS stack.
- Prepared test infrastructure (deployment, automated testing suite, test structure).
- Integrated with third-party services and analytics.
- Reworked part of the API to serverless (multi-tier AWS Lambda, DynamoDB, RDS).
- Modernized the AWS deployment approach.
Technologies: API Design, Redis, Kue, CouchDB, Express.js, Node.jsLead Back-end Developer
2018 - PRESENTDataMeetPeople- Migrated an old RoR back end to Flask and MongoDB (via MongoEngine).
- Developed industrial controller data gathering.
- Added UI dashboard using Vue.js and fixed the existing front end.
- Built PostgreSQL DB schema.
- Added data exchange between analytics and real-time data grabbing back ends.
Technologies: WebSockets, Vue, MongoDB, PostgreSQL, Aiohttp, Flask, PythonDesktop App Developer
2017 - PRESENTAsgard Tutor- Designed the API schema.
- Developed the desktop application using Qt 4.
- Added communication to API server.
- Migrated the desktop application to Qt 5.
- Added client-side data storage (initially JSON then migrated to SQLite).
- Supported the app for clients and added new features.
Technologies: SQLite, Cairo, GTK+, Boost, C++, QtFull-stack Engineer
2020 - 2020Ubindi- Added Stripe integration to Vue-based project and appropriate back-end code.
- Added teacher dashboard controls like policy and acceptance workflow and user data update.
- Added dashboard changes promotion to Stripe (when applicable, like currency).
Technologies: Amazon Web Services (AWS), PostgreSQL, AWS, Elixir, VueFull-stack engineer
2019 - 2020BetterVentures- Developed the back end for a custom printing application.
- Planned and implemented database models' design. Added a MongoDB schema migrations' infrastructure.
- Added administrative dashboard pages for products, orders, and printers' management.
- Performed code review and refactored legacy or invalid code.
- Added a CircleCI automated test and its integration to the app.
- Added automated code linting and testing before commit.
- Managed a unit testing infrastructure with code refactoring (to make it testable) and mocking (to avoid database or third-party services calls).
- Introduced ElasticSearch integration and reporting.
Technologies: Data Migration, Docker, Unit Testing, Apollo, Apollo Server, GraphQL, APIs, MongoDB, JavaScriptFront-end Developer
2019 - 2020Caplena GmbH- Created a reusable chart component and a custom HTML canvas-based chart.
- Reviewed and refactored Vuex structure to make it clear and avoid "magic strings."
- Added a library of wrappers for Vuetify to match project requirements.
Technologies: APIs, ECharts, Apache, Vuetify, VueReact Native Lead Developer
2019 - 2020Medera.ai- Designed an API for remote medical diagnosis to be served from AWS Lambda.
- Created and maintained an API by specs using Python/Chalice.
- Built a React Native client for authentication and API calls.
- Migrated a React Native app to Expo and partially re-implemented a messaging system.
- Added OAuth sign in/sign up to a Lambda-based application.
- Deployed the back and front end to an AWS infrastructure (AWS Lambda, DynamoDB, Route53, and more).
Technologies: APIs, Node.js, Redux, React NativeTeam Leader and Lead Full-stack Developer
2019 - 2019Oxstreer- Reworked a legacy Express.js code for a set of services on the back end.
- Added a new inter-services communication layer with Autodiscovery.
- Rewrote the administrative dashboard from scratch (increasing performance, pagination for large datasets, bug fixing).
- Performed review of React-based shop and prepared list of points to improve.
- Reviewed the UI and added some pixel works for different screen sizes.
- Added the shopping cart module for application using reusable React components.
- Refactored Redux-related modules to remove "magic strings."
- Managed weekly meetings, tracked app development progress.
- Managed the AWS deployment procedure and pipeline automation.
Technologies: Amazon Web Services (AWS), React Redux, React, Docker, ECS, AWS ECR, AWS, Microservices, Node.jsLead Front-end Developer
2019 - 2019San Francisco - Project Evident (via Toptal)- Supported data extraction and translation from the blogging platform to a custom format.
- Improved the UI/UX of a React-based application.
- Enhanced a Gatsby/Ghost plugin to extract data in an adjusted format.
- Rewrote and optimized GraphQL queries for data fetching.
Technologies: React Redux, GraphQL, Netlify, JavaScript, Ghost, Gatsby, ReactLead Full-stack Developer
2019 - 2019Pivotal IO- Designed and structured the overall project management tool.
- Prepared recommendations on tooling and packages.
- Implemented part of the back end.
- Supervised a team of back and front-end developers.
- Migrated the application UI from Vue-Bootstrap to Vuetify.
- Maintained the application after going to alpha version.
- Created a React Native client for an existing API.
Technologies: Amazon Web Services (AWS), Express.js, MySQL, Bootstrap, Vuetify, Vue, Node.jsFull-stack and Blockchain Developer
2018 - 2019Pukkamex, LLC- Prepared architecture and design for a cryptocurrency copy-trading portal.
- Designed an API for a copy trading portal.
- Implemented an API according to specs and hardened it against potential security issues.
- Created a responsive React front end.
- Added real-time Dataflow via WebSockets.
Technologies: Blockchain, Amazon Web Services (AWS), React Redux, Docker, Online Payments, AWS, Trading, Cryptocurrency, APIs, React, Express.js, Node.jsLead Developer
2018 - 2019Primebet (Fractional Media)- Implemented smart contracts from scratch to provide a sports betting feature.
- Optimized Ethereum smart contracts to minimize consumed gas.
- Developed communication between the Ethereum network and the Node.js back end.
- Developed a multi-tier back end to maintain sport games, scores, bidders, and outcome calculation.
- Created a React front end for a sports site.
- Implemented integration with third-party APIs (SportRadar, FantasyData).
- Created background workers to keep data up to date.
- Created deployment procedures and scripts to promote the app to Amazon infrastructure.
Technologies: Blockchain, Amazon Web Services (AWS), React Redux, Docker, Online Payments, AWS, Smart Contracts, Solidity, Ethereum, React, Express.js, Node.jsNode.js Developer
2018 - 2019MyFocus, LLC (via Toptal)- Created a distributed file sharing system based on modified BitTorrent/Kademlia protocol.
- Added different network transport layers like UDP4, UDP6, and Bluetooth.
- Redesigned and created file splitting and hashing to promote to network.
- Added file discovery methods and multi-regional support for faster content retrieval.
Technologies: Blockchain, Distributed Computing, LevelDB, Prototyping, TypeScript, Node.jsSenior React/Preact Engineer
2018 - 2019404publishing (via Toptal)- Optimized Preact SSR rendering time.
- Implemented an API to access dynamically changed data.
- Created and maintained the WebSocket communication layer with reconnections, heartbeat, and data consistency check.
- Created and maintained a mesh network based on WebSocket with dynamic node discovering and connection check.
Technologies: React Redux, APIs, MongoDB, Preact.jsNode.js Back-end Developer
2018 - 2018AirBolt (via Toptal)- Maintained the back end.
- Implemented the database cleanup.
- Reviewed and improved security.
- Reviewed code.
Technologies: Amazon Web Services (AWS), Hapi.js, Node.jsFull-stack Developer
2018 - 2018Popchest (via Toptal)- Provided full-node support and multi-tier deployment support for Bitcoin.
- Fixed Bitcoin-related issues.
- Implemented a new payment feature.
- Implemented tests for Bitcoin and wallets.
Technologies: Amazon Web Services (AWS), Blockchain, AWS S3, AWS, MongoDB, Express.js, Node.js, BitcoinBack-end Python Engineer
2017 - 2018Successkit.io (via Toptal)- Supported the Python back end.
- Improved database migration scripts via Alembic.
- Fixed PostgreSQL-specific issues in the database layer.
- Improved and extended existing functionality.
- Added PDF export of reports.
- Extended existing React controls to reflect back-end changes.
Technologies: Amazon Web Services (AWS), React, PDF, PostgreSQL, SQLAlchemy, Alembic, Flask, PythonEthereum Developer
2017 - 2018SilverToken (via Toptal)- Implemented smart contracts and tokens.
- Implemented back-end features using Express.js with JWT authentication.
- Tested pre-ICO technology.
- Launched and maintained the ICO.
- Migrated and optimized contracts.
Technologies: Express.js, Node.js, Truffle, EthereumEthereum and Back-end Developer
2017 - 2018OG Mobi (via Toptal)- Gathered requirements for smart-contract and back-end code.
- Developed a smart contract to collect ether and store jackpot players.
- Built the back end for the site.
- Created a front-end prototype that worked with both the back end and contract events using React.
- Prepared deployment documentation for the site (deployed on Heroku) and Ethereum standalone mode.
- Generated a contract management dashboard.
- Conceived minor specific UI controls for the front end using React, like lottery wheel, carousel, among other playing features.
Technologies: React, Express.js, Node.js, Truffle, EthereumSoftware Developer
2017 - 2017AirBolt, Pty., Ltd. (via Toptal)- Enhanced an authentication service in a Node.js application empowered with Hapi.
- Maintained a MongoDB database, fixed consistency, and added constraints.
- Added the administrative part using React for the front end over the existing API.
- Extended the API for the administrative part.
- Prepared deployment and maintenance documentation.
- Refactored and cleaned up the code.
Technologies: Amazon Web Services (AWS), Amazon EC2, AWS S3, Hapi.js, Node.js, MongoDBFreelance Full-stack Developer
2017 - 2017The Vaan Group (via Toptal)- Created an audio guide plugin for forms.
Technologies: AWS S3, Heroku, CSS3, Bootstrap, HTML5, Web Audio API, Django, Python 3Node.js Developer
2017 - 2017Algolibs- Developed a color search engine that allows users to get images relevant to one or more colors.
- Created image collectors to gather sample data (at least a million images' worth of data) stored in MongoDB from existing images.
- Extended color search engine to allow search by hue value (median).
- Prepared deployment documentation.
Technologies: MongoDB, jQuery, Express.js, Node.jsFreelance Python Developer
2016 - 2017Forecastly (via Toptal)- Added an Amazon Inbound Shipment fulfillment interface to www.github.com/czpython/python-amazon-mws.
- Supported the site using Flask, Bootstrap, and Flask-Bootstrap packages.
- Refactored and cleaned up code.
- Provided a suggestion for migration from Pony ORM to SQLAlchemy, pointing to potential caveats and bonuses according to the customer's requirements.
Technologies: REST APIs, Amazon MWS, Flask, PythonBack-end API Developer
2016 - 2016NDA- Created an API with OAuth for the existing site to provide desired data externally.
- Secured the API with request rate and IP per minute.
- Developed key infrastructure and UI dashboard to help users maintain access keys and secrets.
- Added automated deployment scripts.
- Maintained existing back-end code and database (PostgreSQL).
- Embedded API intermediate results caching using Redis.
Technologies: PostgreSQL, Caching, Redis, Webpack, Bootstrap, Knockout.js, Express.js, Node.jsFreelance Lead Python Developer
2016 - 2016Pickett (via Toptal)- Prepared technology stack suggestions. Developed site and database architecture documents.
- Created the site using Python/Flask and MySQL.
- Supported UI according to design guidelines.
- Added a database migration engine and supported multiple database branch migration processes.
- Introduced tests (WebDriver and PyUnitTest) and covered the entire application.
- Appended a data scraper from different sources (HTML pages and APIs).
- Prepared multi-tier deployment documentation and supported automatic deployment to Amazon EC2 instances.
- Optimized Amazon instance performance and cost.
Technologies: Amazon Web Services (AWS), AWS S3, Amazon EC2, AWS, MySQL, Bootstrap, jQuery, Flask, PythonFreelance Programmer
2015 - 2016Medify, Ltd. (via Toptal)- Modified the Anki flashcard app to help users concentrate on their weakest topics.
Technologies: PyQtSenior Python Developer
2014 - 2016Steppechange- Created a UI for user management.
- Developed an engine for static content handling.
- Maintained a back-end application.
- Introduced asset bundling and versioning.
- Implemented a preview of Windows 8 tiles for different modes (cycle, slide, flip, etc.) via jQuery and jQueryUI.
Technologies: PyMongo, MongoEngine, MongoDB, Flask, Python, Push NotificationsBack-end API Developer
2015 - 2015Perigee- Assembled API specifications and protocols.
- Set up the environment and automatic deployment script.
- Prepared tests for future API endpoints and methods (integration and unit tests).
- Created an API server according to specs and tests.
- Adjusted the API to meet iOS app requirements.
- Made some change requests to improve application functionality.
- Worked closely with the front-end team to fix issues.
Technologies: SQLAlchemy, Flask, PythonTechnical Leader
2010 - 2014Exigen Services/Return on Intelligence- Created and maintained the UI for management of client bonus and benefit groups.
- Refactored database structure. Introduced Entity Framework to the application. Fixed bottlenecks in requests.
- Added client-side validation via jQuery validation.
- Maintained unit tests.
- Optimized SQL scripts.
Technologies: Oracle, Microsoft SQL Server, Durandal, ASP.NET, C#C# Developer
2007 - 2008Astra Software- Implemented a thick client.
- Provided coverage for unit tests.
- Reviewed code.
- Developed Asterisk modules.
- Introduced logging via a logging application block.
Technologies: Microsoft Enterprise Library, C#, .NET