• Developed a set of APIs to manage donation partners' and customers' data.

• Implemented a new customer onboarding procedure and seamlessly integrated it into existing web portals.

• Developed customer website and administrative dashboard.

• Created and supported Web3 check and safety mechanisms and rules to prevent phishing, scams, and other malicious actions against users.

• Developed Safari extension to communicate between blockchain and hardware wallet

• Added new pages to the Safari web extension that supported secure transaction signing.

• Supported a payment system that involved complex analytics companion service.

• Maintained an analytics service to collect and combine payment results.

• Supported a payment system while expanding to new markets in Asia.

• Updated and refreshed Swagger API documentation and contract.

• Maintained the Node.js back end with hardened security aspects.

• Added new features to the back end to meet business requirements due to expansion to new markets in Thailand, Indonesia, and the Philippines.

• Developed data extraction and translation from the blogging platform to a custom format.

• Developed of a React front-end

• Enhanced a Gatsby/Ghost plugin to extract data in an adjusted format.

• Maintained the Node.js back end powered by CompoundJS. Supported deployments to AWS Elastic Beanstalk.

• Planned a new API structure, introduced versioning, and added security control.

• Migrated the old code to a modern runtime and added the appropriate fixes to run on the latest version of Node.js.

• 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.

• 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.

• Reworked 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, providing pagination for large datasets, bug fixing).

• 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).

• Designed and structured the overall project management tool.

• Prepared recommendations on tooling and packages.

• Implemented part of the back end.

• Migrated an old RoR back end to Flask and MongoDB via MongoEngine.

• Added a UI dashboard using Vue and fixed the existing front end.

• Developed an API and protocol for industrial controller data collection.

• Added data exchange between analytics and real-time data-grabbing back ends.

• Built a PostgreSQL database schema and introduced a migration-based approach.

• 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.

• 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.

• 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.

• 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.

• Designed an API schema and security aspects as a Swagger-based file.

• Developed the desktop application using Qt 4 for end users.

• Added communication to API server with authorization and authentication mechanism.

• Migrated the desktop application to Qt 5 after it was released to production.

• Added client-side data storage, initially JSON, and then migrated to SQLite.

• Supported the app for clients and added new features.

• 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.

• 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.

• 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.

• 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.

Modified the Anki flashcard app to help users concentrate on their weakest topics.

• Developed entire user management back- and front-ends

• Developed an engine for static content handling.

• Maintained a back-end application.

• 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.

• Added localization support to the existing back end powered by Django.

• Refactored the legacy Django API, i.e., Django REST service.

• Discussed and suggested new approaches to client-server communication and decreased traffic by 30%, according to the back-end logs.

• Maintained a public website and added new sections and pages.

• Added Stripe integration to Vue-based project and corresponding back-end code.

• Improved the dashboard by adding changes to Stripe promotions, such as currency, when applicable.

• Added teacher dashboard controls such as policy and acceptance workflow and user data updates.

• Maintained the back end.

• Implemented the database cleanup.

• Reviewed and improved security.

• Reviewed code.

• 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.

• 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.

Created an audio guide plugin for forms.

• 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.

• 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.

• 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.

• 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.