Denys Pasishnyi, Developer in Barcelona, Spain
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Denys Pasishnyi

Verified Expert  in Engineering

Software Developer

Barcelona, Spain
Toptal Member Since
September 25, 2020

Denys is a software engineer who loves working with open-source technology. He has over ten years of comprehensive expertise developing microservices, APIs, server and CLI tools, websites, web crawlers, and mobile and desktop applications across business sectors, including eCommerce, marketing, fintech, and stocks. Denys is passionate about readable, maintainable, and testable code. He excels at leading teams in Agile and enjoys working with Go.


Go, PostgreSQL, WebSockets, Docker, Kubernetes, Google Cloud Platform (GCP)...
Amazon Web Services (AWS), AWS Lambda, Amazon DynamoDB, Redis, Amazon Cognito...
Vue, Linux, Windows, MacOS, Confluence, Jira, Git, Docker, Bash, PostgreSQL...




Preferred Environment

Go, Amazon Web Services (AWS), Docker, MySQL, PostgreSQL

The most amazing...

...thing I've implemented was the back end for TEE with DUKPT for processing NFC transactions for mobile a POS.

Work Experience

Senior Software Engineer

2022 - 2023
  • Implemented AML screening of blockchain addresses with notification.
  • Refactored the platform to simplify 3rd-party application management.
  • Implemented multi-chain support and part of the cross-chain transaction feature.
  • Fixed and made improvements in transaction flows, OAuth, etc.
  • Implemented API automatic testing with the Postman test script.
Technologies: Go, PostgreSQL, WebSockets, Docker, Kubernetes, Google Cloud Platform (GCP), Web3, REST APIs, Microservices, GitHub, APIs

Senior Software Engineer

2020 - 2022
  • Implemented the back end for TEE with DUKPT for processing NFC transactions for a mobile POS.
  • Developed authentication, authorization, 2FA, and session control on the back and front ends.
  • Performed DocuSign and Amazon WorkDocs integration for contract management.
  • Implemented security measures for banking certifications.
  • Maintained and improved the SWIFT transactions system.
  • Architected an invoice management service on the back end.
Technologies: Amazon Web Services (AWS), AWS Lambda, Amazon DynamoDB, Redis, Amazon Cognito, AWS Step Functions, Amazon S3 (AWS S3), AWS CloudFormation, JavaScript, Vue, Jira, Lambda Architecture, Unit Testing, Go, NoSQL, Amazon Simple Email Service (SES), Amazon Simple Notification Service (Amazon SNS), DocuSign, REST APIs, Microservices, GitHub, Amazon Simple Queue Service (SQS), Amazon EventBridge, Full-stack, Node.js, APIs

Senior Software Engineer

2019 - 2020
  • Maintained and created new Go CLI tools for SEO and internal administration.
  • Developed GUI for Go tools usage under Linux/macOS/Windows.
  • Improved permissions verification for distributed Go tool usage and automatized distribution.
  • Implemented an API of Google Search Console, Microsoft Azure, and Jira.
Technologies: Vue, Linux, Windows, MacOS, Confluence, Jira, Git, Docker, Bash, PostgreSQL, Laravel, PHP, Electron, Node.js, Sass, CSS, HTML, JavaScript, Go, Full-stack, Minimum Viable Product (MVP)

Senior Software Engineer

2018 - 2019
Actelligent Group
  • Participated in MVP development, creating microservices and a JSON API.
  • Developed functionality to get stock details and organize events and private sessions.
  • Analyzed and used data from a FactSet database of more than 4GB.
  • Optimized the performance of the SQL database and queries.
  • Collaborated with the data science team for data extraction from the FactSet database.
  • Developed data import from a 3rd-party API and XLSX documents.
Technologies: Amazon Web Services (AWS), Microservices, Unit Testing, GitHub, Git, MySQL, WebSockets, gRPC, Kubernetes, Docker, Go, REST APIs, CircleCI, Minimum Viable Product (MVP), APIs

Senior Software Engineer

2017 - 2018
Blocktech Services
  • Participated in the MVP development, creating microservices and a REST API for Pungo Token.
  • Improved code quality and performance of data collectors from external APIs.
  • Implemented Agile methodologies and created internal coding standards.
  • Supervised blockchain development on the Komodo platform.
Technologies: Microservices, REST APIs, Unit Testing, Silex, PHP, WebSockets, GitLab CI/CD, GitLab, Git, Docker, gRPC, Redis Queue, Redis, MariaDB, Go, NoSQL, MySQL, Minimum Viable Product (MVP), APIs

Full-stack Developer

2015 - 2016
  • Developed employer management and social interactions in the back and front ends.
  • Created and improved many internal and public REST API endpoints.
  • Refactored a tracking system with Mixpanel, improving code quality and adding features.
  • Integrated product migration to eBay, Amazon MWS/Advertising, and Google Shopping.
  • Contributed to the adaption of several Agile methodologies.
Technologies: REST APIs, GitHub, Git, Backbone.js, Docker, Redis, MariaDB, Symfony 2, PHP, NoSQL, MySQL, Full-stack, APIs

Senior Full-stack Developer | Scrum Master

2014 - 2015
  • Developed several important features following high-quality standards and Agile methodologies.
  • Managed a team as Scrum Masters and implemented Scrum of Scrums.
  • Contributed to the implementation of domain-driven design in the main application.
  • Made a more customizable email-sender microservice.
  • Developed user behavior counter (over 300 000 requests per day).
  • Integrated the API of Zendesk, Mixpanel, Intercom, and Segment.
Technologies: Amazon Web Services (AWS), Microservices, REST APIs, Unit Testing, New Relic, Kibana, Confluence, Jira, GitHub, Git, Jenkins, C, jQuery, CoffeeScript, JavaScript, Go, Docker, Redis, MySQL, Symfony 2, PHP, NoSQL, APIs

Back-end Developer

2012 - 2014
  • Participated in MVP development of the social network Pinroom. It is similar to Pinterest.
  • Developed several features in Fancybox (PrestaShop).
  • Participated in the development of an eCommerce base (Symfony), which evolved into an Elcodi open-source project.
  • Developed Chick Place based on the created eCommerce base.
  • Participated in the creation of a payment gateway open-source plugin (Symfony) and integrated Stripe, Google Wallet, and
Technologies: Amazon Web Services (AWS), Behavior-driven Development (BDD), Redis Queue, Symfony 2, PrestaShop, Functional Testing, Unit Testing, Redmine, Varnish, Selenium, Jenkins, Vagrant, GitHub, Git, jQuery, JavaScript, Elasticsearch, Redis, MySQL, PHP, NoSQL, Minimum Viable Product (MVP)

Full-stack Developer | Team Leader

2011 - 2012
  • Directed the migration from OsCommerce to Magento and from Visual Basic to Symfony.
  • Maintained and developed new features for AndorraFreeMarket eCommerce.
  • Developed three times faster stock importing process that allowed the addition of more stocks and selling this data as an additional service of the AndorraFreeMarket.
  • Managed a team of four developers and coordinated projects directly with clients.
  • Extended functionality of the click line (Magento) and integrated ASM, GLS, Nacex, Parcel, and TNT.
Technologies: Git, CSS, HTML, jQuery, JavaScript, MySQL, Magento, Symfony 2, PHP, Full-stack

Full-stack Developer

2008 - 2010
JAD Solucions
  • Participated in the development of an e-learning platform via questionnaires for FECIC.
  • Created several websites based on the internal CMS with custom functionality.
  • Improved the internal CMS, making its front end more customizable.
Technologies: Mantis, Subversion (SVN), CSS, HTML, JavaScript, Symfony, PHP, Full-stack

FECIC Learning Platform
I participated in the development of an internal e-learning platform on the base of Symfony FECIC. The learning process was aided by the use of questionnaires. These led to the certification of company workers.


I directed four developers and participated in the migration from OsCommerce to Magento, as the front-end platform, and from VisualBasic to Symfony, as the product's administration panel.

I was in direct contact with the client and workers, especially forimplementingf the administration panel. I created a faster stock importing process that allowed one to add more stocks and sell this data as an additional service through the REST API.


I assisted in the creation of an eCommerce platform based on Symfony 2. I then adapted the eCommerce platform for Chicplace-a marketplace for unique products from charming shops in Spain, France, and Italy. The eCommerce base, which later evolved into the Elcodi open-source project

I created a cutting-edge Android app with related services to read and listen to text RSS feeds as music. Developed the REST API for a website, Android app, Chrome extension, and a website and Chrome extension for feeds management. This project is currently inactive. However, the code is available on GitHub.

Paymentsuite for Symfony
I participated in the creation of a generic payment gateway for Symfony. It's an open-source product, which provides the easy implementation of payment gateways with events for payment stages. I developed integrations for Stripe, Google Wallet, and Authorize.Net.
2008 - 2010

Bachelor's Degree in Computer Science

IES Carles Vallbona - Granollers, Spain


REST APIs, JSON API, Vue, jQuery, Backbone.js, Redis Queue, Node.js


GoLand, Git, GitHub, Subversion (SVN), Mantis, Vagrant, Jenkins, Varnish, Redmine, PrestaShop, Jira, Confluence, Kibana, GitLab, GitLab CI/CD, Amazon Cognito, AWS Step Functions, AWS CloudFormation, Amazon Simple Email Service (SES), Amazon Simple Notification Service (Amazon SNS), CircleCI, Amazon Simple Queue Service (SQS)


Symfony 2, Symfony, .NET, Selenium, gRPC, Silex, Electron, Laravel, Android SDK


Go, SQL, Java, C, PHP, JavaScript, HTML, CSS, CoffeeScript, Sass, Bash


Unit Testing, Microservices, Functional Testing, Behavior-driven Development (BDD), Lambda Architecture


MySQL, Redis, Elasticsearch, MariaDB, PostgreSQL, Amazon DynamoDB, Amazon S3 (AWS S3), NoSQL


Linux, Docker, Magento, New Relic, Kubernetes, MacOS, Windows, Firebase, Magento 2, Amazon Web Services (AWS), AWS Lambda, Google Cloud Platform (GCP)


Networks, WebSockets, Android Wear, Chrome Extensions, Serverless, DocuSign, APIs, Web3, Amazon EventBridge, Full-stack, Minimum Viable Product (MVP)

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