Mateusz Dominiak, Developer in Warsaw, Poland
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Mateusz Dominiak

Verified Expert  in Engineering

Ruby on Rails Developer

Location
Warsaw, Poland
Toptal Member Since
December 13, 2014

Matt is a senior web developer and architect with sixteen years of experience. His core competency lies in end-to-end architecting and development of web applications through all phases from the ground up. He has a proven track record of successful product launches working remotely for technology startups for the past eleven years.

Portfolio

Freelance
Ruby on Rails (RoR), JRuby, Java, Python, PostgreSQL, Citus, Sidekiq, Redis...
Jungle Scout
Ruby on Rails (RoR), Ruby on Rails 5, Stripe API, Stripe Connect API...
Diagnotes, Inc.
Ruby on Rails (RoR), Ruby, Resque, PostgreSQL, RSpec, Pgcrypto, Capybara...

Experience

Availability

Part-time

Preferred Environment

Amazon Web Services (AWS), Sublime Text 3, Visual Studio Code (VS Code), Docker, Git, MacOS, DataGrip, CircleCI, Pivotal Tracker, Slack

The most amazing...

...thing I've built is a multi-threaded server collecting telemetry measurements from remotely deployed sensors with a low-footprint custom communication protocol.

Work Experience

Senior Ruby on Rails and Node.js Developer

2020 - 2022
Freelance
  • Implemented high-performance bots for arbitrage and market-making on centralized and decentralized cryptocurrency exchanges.
  • Developed a dynamic distributed algorithm for efficient backtesting of automated Forex trading strategies over a large volume of historical data.
  • Designed distributed sharded database for efficient querying and storage of billions of records. Implemented import of tick, bar, and indicator data from third-party Forex feeds.
  • Built reporting dashboards and charts with React and TradingView.
Technologies: Ruby on Rails (RoR), JRuby, Java, Python, PostgreSQL, Citus, Sidekiq, Redis, Stimulus, Haml, HTML, SCSS, CSS, Highcharts Stock, Highcharts, Docker, Amazon Elastic Container Service (Amazon ECS), AWS CloudFormation, CircleCI, Node.js, TypeScript, React, TradingView, MongoDB, Amazon EC2, Jest, DevOps

Senior Ruby on Rails Developer

2018 - 2019
Jungle Scout
  • Launched a marketplace platform based on open-source Sharetribe for Amazon Freelancers offering services to Amazon Sellers.
  • Implemented complex Stripe integration for a marketplace charging service and processing fees using managed and custom Stripe accounts, on-behalf charges, transfers, payouts, and partial and full refunds.
  • Developed multi-step checkout and abandoned cart notifications, which led to improved sales.
  • Built a highly demanded attachments feature for freelancer-client chat, which quickly grew to hundreds of thousands of files stored in and served from AWS S3.
  • Integrated Google Tag Manager and Google Analytics with custom dimensions, metrics, and events to measure the impact of rolled-out features.
  • Built a listing WYSIWIG editor based on Basecamp's open-source Trix to improve the quality of listings.
  • Redesigned the front-end according to brand guidelines. Used Litmus to improve HTML email templates to be responsive and support a wide range of email clients, including Outlook.
  • Introduced Cypress end-to-end acceptance tests and improved unit test coverage.
  • Implemented Stripe charge metadata for accounting and financial reports in Stripe Sigma.
  • Contributed to the upstream open-source Sharetribe project with bug fixes.
Technologies: Ruby on Rails (RoR), Ruby on Rails 5, Stripe API, Stripe Connect API, Stripe Sigma, Stripe, Sphinx Search Engine, Memcached, Pundit, OmniAuth, Facebook Login, Google Login, Google Places API, Google Analytics API, ActiveCampaign, Devise, Delayed Job, iDevAffiliate API, Amazon S3 (AWS S3), Amazon Simple Email Service (SES), Amazon Aurora, MySQL, Amazon CloudFront CDN, Heroku, RSpec, Cypress, Sentry, JavaScript, React, Node.js, SCSS, Haml, Bootstrap, Chrome Extensions, CircleCI, DevOps

Senior Ruby on Rails Developer

2015 - 2017
Diagnotes, Inc.
  • Developed a HIPAA-compliant healthcare text, audio, and video communication platform for medical providers and patients.
  • Built web video chat and encrypted video archiving.
  • Created and integrated an ActiveRecord library for efficient and seamless data encryption and decryption using Pgcrypto and AWS KMS.
  • Built LDAP authentication and synchronization of ActiveDirectory users, and also SAML SSO with ADFS.
  • Implemented tree-based user group hierarchy with inherited permissions and efficient ways of querying them utilizing the materialized path pattern.
  • Introduced browser-driven end-to-end acceptance tests and contributed to overall test coverage boost up to 94%.
  • Worked on a RESTful JSON API consumed by iOS and Android client applications.
  • Migrated the application from Rails 4 to Rails 5.
Technologies: Ruby on Rails (RoR), Ruby, Resque, PostgreSQL, RSpec, Pgcrypto, Capybara, Amazon S3 (AWS S3), AWS Key Management Service (KMS), Amazon Simple Notification Service (Amazon SNS), Amazon Simple Email Service (SES), Elasticsearch, Amazon CloudFront CDN, Redis, OpenTok, Pusher, Flowplayer, SemaphoreCI, New Relic, JavaScript, React, jQuery, Haml, Sass, CSS3, Bootstrap, Bootstrap 3, DevOps

Senior Ruby on Rails Developer

2014 - 2015
Unityaid Pty, Ltd.
  • Led the development of a crowdfunding web application to successful launch in five months.
  • Integrated Stripe Connect and credit card processing on behalf of merchant accounts which also involved support for multiple countries and currencies and refund processing using Stripe webhooks.
  • Created a dashboard to monitor campaign progress and manage contributions.
  • Developed and maintained an extensive integration and browser test suite covering major application features and workflows.
  • Implemented a responsive UI, which proved to be a breaking point for the application as 66% of visitors are smartphone and tablet users.
Technologies: Ruby on Rails (RoR), CoffeeScript, jQuery, Haml, HTML5, Sass, CSS3, Bootstrap, Sidekiq, PostgreSQL, RSpec, Capybara, Selenium WebDriver, Backbone.js, Amazon S3 (AWS S3), Amazon CloudFront CDN, Redis, Heroku, Facebook API, X (formerly Twitter) API, New Relic

Lead Ruby on Rails Developer

2011 - 2013
OK Venue, LLC
  • Created a web application to create and manage events and sell tickets. Managed a successful product launch: hosting of New York SOHO International Film Festival screenings in 2013.
  • Implemented a QR code ticket generation mechanism and ticket delivery via email (Postmark API), text message (Twilio API), and picture message (Mogreet API). Created and open-sourced a Ruby Gem for sending picture messages (MMS) with Mogreet.
  • Integrated secure credit card processing with Braintree API using client-side encryption. Integrated ACH payments with Transmodus API, allowing event owners to withdraw ticket sales income.
  • Architected and implemented REST microservices and embeddable Rails::Engine modules allowing for white labeling of the product.
  • Implemented short URL tracking and analytics allowing event curators to identify the most efficient marketing campaigns, channels, and tastemakers.
  • Led the development of a web application for activating and managing decoupled debit cards.
Technologies: Ruby on Rails (RoR), CoffeeScript, jQuery, Haml, HTML5, Sass, CSS3, Bootstrap, Delayed Job, PostgreSQL, MySQL, RSpec, Capybara, Selenium WebDriver, Twilio API, Facebook API, X (formerly Twitter) API, Linode, Cloudflare, New Relic, Airbrake, QR Codes

Senior Ruby on Rails Developer

2008 - 2012
MD Consulting
  • Created a web application for analyzing arbitrary multi-dimensional data using OLAP cubes.
  • Developed a customizable dashboard for visualizing and analyzing complex financial data.
  • Created custom UI web components using a Raphael JS library.
  • Advised on the design and implementation of TextMagic API and Ruby wrapper library for sending text messages.
  • Implemented a web scraper for importing and synchronizing job listings from http://nav.no into a Scandinavian job search index.
  • Created a Facebook quiz application for Richmond University to help future students select their major subject based on quiz answers.
Technologies: Ruby on Rails (RoR), JRuby, Ruby, CoffeeScript, jQuery, Backbone.js, Raphaël, HTML5, Haml, CSS3, Sass, Bootstrap, OLAP, Pentaho Mondrian OLAP Engine

Ruby on Rails Developer

2009 - 2011
SmartSites, LLC
  • Created a web application for grading and improving resumes.
  • Implemented a scoring and profiling algorithm based on uploaded resume documents.
  • Created a Ruby gem and web service hosted on Windows Server for analyzing MS Word documents using Win32 OLE interface.
  • Developed a web application for creating online resumes.
Technologies: Ruby on Rails (RoR), JavaScript, HTML, CSS, Delayed Job, CanCan, Haml, Liquid, Airbrake, Capistrano, Factory Girl, Paperclip, Nokogiri

Ruby on Rails Developer

2010 - 2010
Netronix, Inc.
  • Developed a web application for remote monitoring of environmental data (including weather, wind, water quality, temperature, flow, and depth).
  • Led the transition of a beta product to production state with its first paying customers.
  • Created a multi-threaded Ruby server listening for measurement data sent by remote sensors over Iridium satellite. The costly satellite bandwidth required the development of a custom low-footprint communication protocol over TCP/IP.
  • Implemented a customizable dashboard with real-time charts displaying incoming telemetry data.
  • Provided a module allowing the user to remotely configure sensors via the web interface.
  • Implemented alert rules and notification via SMS and/or email (like water depth at node y > x).
Technologies: Ruby on Rails (RoR), Ruby, HTML, Sass, CSS, JavaScript, Highcharts, Prototype Framework, Airbrake, Capistrano, Twilio API

Senior Ruby on Rails Developer

2009 - 2010
Umongous, Inc.
  • Developed the back end of a web application for online surveys.
  • Implemented an anti-bot mechanism preventing bots from taking surveys.
  • Created a logic and administration interface for demographic surveys.
  • Redesigned key database schema entities and ActiveRecord objects for better maintainability.
  • Optimized MySQL queries for high-traffic requirements using MySQL slow logs.
Technologies: Ruby on Rails (RoR), JavaScript, jQuery, MySQL, HTML, CSS

J2EE Designer and Developer

2007 - 2008
Infovide-Matrix
  • Developed a functional tester in Eclipse RCP for a telecommunication company.
  • Implemented a Corba-to-XML and XML-to-Corba object mapper based on XML Schema and IDL files.
  • Wrote a mechanism for rendering message input forms in Eclipse RCP based on XML Schema.
  • Designed and implemented a web application supporting recruitment workflow (WebSphere Business Modeler, WebSphere Integration Developer, WebSphere Process Server).
Technologies: Java, Jakarta EE, IBM WebSphere, Eclipse RCP, Eclipse Modeling Framework (EMF), XML Schema, CORBA

Java Developer in Pricing and Workflow

2006 - 2007
J.P. Morgan Chase
  • Developed a complex Eclipse RCP option pricer application in the equity exotics and hybrids department.
  • Conducted workflow modeling and implementation in BEA AquaLogic BPM.
  • Designed and implemented a client-server application for publishing financial instruments.
  • Integrated the client application with an external workflow server.
  • Worked in Agile methodology involving daily scrums.
Technologies: Java, Jakarta EE, Eclipse RCP, JUnit, Spring, BEA AquaLogic Service Bus, XML

J2EE and PL/SQL Developer

2004 - 2006
Syndatis
  • Designed and developed business process management (BPM) web applications that implement contract and expense workflows for pharmaceutical companies.
  • Designed and implemented a module for the reconciliation of employee American Express credit cards.
  • Analyzed business workflows and prepared functional and technical specifications in Waterfall methodology.
Technologies: JavaScript, CSS, HTML, Apache Velocity, Torque, Jakarta EE, Microsoft SQL Server, Oracle RDBMS, PL/SQL

Hotwire Chat

https://github.com/mdominiak/hotwire-chat
Hotwire Chat is a demo chat web application built in Ruby on Rails and Hotwire. I built it to demonstrate navigation with Turbo Drive, page decomposition with Turbo Frames, broadcasting updates with Turbo Streams via ActionCable WebSocket, and optimization of rendering time by caching HTML partials with Redis cache store. The key actions and flows are accompanied by integration and system tests.

Jungle Scout Market

Jungle Scout Market is a marketplace platform based on open-source Sharetribe for Amazon Freelancers offering services to Amazon Sellers. I was a full-stack Ruby on Rails developer responsible for successfully launching the project, continuously implementing, deploying, and monitoring new features, working closely with the product manager, CTO, and customer support.

Diagnotes

https://www.diagnotes.com
A web application for secure healthcare communication.

OK Venue

https://okvenue.com
A web application for creating events and selling tickets.

InstantCashSweepstakes

http://instantcashsweepstakes.com/
A web application for online surveys coupled with online market research web application http://aytm.com.

Environet

https://ienvironet.com/
A web application for remote monitoring in the environment sector.

Utilizing Agent Teams in Grid Resource Brokering | Academic Publication

http://www.ibspan.waw.pl/~paprzyck/mp/cvr/research/agent_papers/MAGS_2007.pdf
M. Dominiak, M. Ganzha, M. Gawinecki, W. Kuranowski, M. Paprzycki, S. Margenov, I. Lirkov, Utilizing Agent Teams in Grid Resource Brokering, International International Transactions on Systems Science and Applications, Vol. 3, No. 4, 2008, 296-306.

Selecting Grid-agent-team to Execute User-job — Initial Solution | Academic Publication

http://www.ibspan.waw.pl/~paprzyck/mp/cvr/research/agent_papers/ARES_2007.pdf
M. Dominiak, M. Ganzha, M. Paprzycki, Selecting grid-agent-team to execute user-job — initial solution, Proceedings of the Conference on Complex, Intelligent and Software Intensive Systems, IEEE CS Press, Los Alamitos, CA, 2007, 249-256.

Efficient Matchmaking in an Agent-based Grid Resource Brokering System | Academic Publication

http://www.ibspan.waw.pl/~paprzyck/mp/cvr/research/agent_papers/wisla_06.pdf
M. Dominiak, W. Kuranowski, M. Gawinecki, M. Ganzha, M. Paprzycki, Efficient Matchmaking in an Agent-based Grid Resource Brokering System, Proceedings of the International Multiconference on Computer Science and Information Technology, PTI Press, 2006, 327-335.

Utilizing Agent Teams in Grid Resource Management ... | Academic Publication

http://www.ibspan.waw.pl/~paprzyck/mp/cvr/research/agent_papers/JVA_06.pdf
M. Dominiak, W. Kuranowski, M. Gawinecki, M. Ganzha, M. Paprzycki, Utilizing agent teams in grid resource management — preliminary considerations, Proceedings of the IEEE J. V. Atanasoff Conference, IEEE CS Press, Los Alamitos, CA, 2006, 46-51.
2001 - 2006

Master of Science Degree in Computer Science

Warsaw University of Technology - Warsaw, Poland

Libraries/APIs

Ruby ERB, Pusher, API Development, Resque, Ruby on Rails API, Nokogiri, CarrierWave, Devise, Highcharts, jQuery, Sidekiq, Stripe, WebRTC, PubNub, React, Twilio API, Braintree API, Selenium WebDriver, OmniAuth, Backbone.js, Raphaël, Delayed Job, Liquid, Stripe API, Stripe Connect API, Pundit, Facebook Login, Google Places API, Google Analytics API, Node.js, Rollbar, Moment.js, D3.js, Google Maps, Paperclip, Facebook API, Mandrill API, Mongoid, X (formerly Twitter) API, PayPal API, Vue

Tools

SemaphoreCI, GitHub, RSpec, NGINX, Google Analytics, AWS SDK, RuboCop, Amazon Simple Notification Service (Amazon SNS), Amazon Simple Email Service (SES), Capistrano, Git, Citus, Amazon CloudFront CDN, Airbrake, Torque, Eclipse RCP, Sublime Text 3, ITerm, Stripe Sigma, Sentry, CircleCI, AWS Key Management Service (KMS), Flowplayer, DataGrip, Pivotal Tracker, Slack, Sublime Text 2, Terminal, Litmus, AWS CloudFormation, Amazon Elastic Container Service (Amazon ECS), Turbo, Webpack, Chef, Amazon ElastiCache, Vagrant, AWS OpsWorks, Cucumber, Pentaho Mondrian OLAP Engine

Frameworks

Ruby on Rails 5, Ruby on Rails 4, Ruby on Rails (RoR), Capybara, Bootstrap, Swagger, OAuth 2, minitest, Jest, Prototype Framework, Factory Girl, Apache Velocity, JUnit, Spring, Eclipse Modeling Framework (EMF), Cypress, Bootstrap 2, Bootstrap 3, Ruby on Rails 3, Stimulus, ActionCable, AngularJS, Angular

Languages

SCSS, Ruby, HTML, SQL, HTML5, Sass, CoffeeScript, CSS3, Haml, CSS, JavaScript, TypeScript, SAML, Java, JRuby, XML, UML, C, C++, Lisp, Haskell, SAS, Python, ECMAScript (ES6), GraphQL

Paradigms

Agile Software Development, REST, DRY, Object-oriented Design (OOD), Test-driven Development (TDD), Microservices, Scrum, Concurrent Programming, OLAP, Database Design, Parallel Programming, Distributed Programming, Software Testing, Continuous Delivery (CD), Microservices Architecture, HIPAA Compliance, Continuous Integration (CI), Continuous Deployment, DevOps

Platforms

OpenTok, Heroku, Twilio, Amazon Web Services (AWS), Linux, Amazon EC2, X (formerly Twitter), Linode, Jakarta EE, WebSphere, OS X, Visual Studio Code (VS Code), MacOS, IBM WebSphere, Docker, New Relic

Storage

Amazon S3 (AWS S3), PostgreSQL, Redis, MySQL, Memcached, PL/SQL, Oracle RDBMS, Microsoft SQL Server, XML Schema, Sphinx Search Engine, Amazon Aurora, Elasticsearch, MongoDB

Other

Ruby Gems, System Architecture, GitFlow, RESTful Web Services, APIs, Fitbit, Cloudflare, Algorithms, Data Structures, Google Tag Manager, Data Encryption, LDAP, Video Calling, Turbolinks, API Design, QR Codes, CanCan, BEA AquaLogic Service Bus, CORBA, Google Login, ActiveCampaign, iDevAffiliate API, Chrome Extensions, Pgcrypto, Artificial Intelligence (AI), Calculus, Algebra, Discrete Mathematics, Probability Theory, Statistics, Software Engineering, Neural Networks, Image Recognition, Speech Recognition, Data Compression, Data-level Security, Highcharts Stock, Computer Science, Information Technology, Hotwire, System Testing, Integration Testing, Caching, GitHub Actions, WebSockets, Authorization, Amazon Route 53, TradingView

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