Denys is available for hire
Hire DenysDenys Pasishnyi
Verified Expert in Engineering
Software Developer
Barcelona, Spain
Toptal member since September 25, 2020
Bio
Denys is a senior software engineer with 18 years of experience building microservices, APIs, and distributed back-end systems, specializing in Go. He recently designed and shipped a production blockchain token-indexing service that improved indexing throughput 10 to 40 times. He's a skilled team leader who champions clean, testable, maintainable code.
Portfolio
Teranode Group
GoLand, gRPC, REST APIs, Neo4j, PostgreSQL, Bitcoin, Amazon OpenSearch...
Monerium
Go, PostgreSQL, WebSockets, Docker, Kubernetes, Google Cloud Platform (GCP)...
Divilo
Amazon Web Services (AWS), AWS Lambda, Amazon DynamoDB, Redis, Amazon Cognito...
Experience
- Go - 10 years
- SQL - 10 years
- Redis - 8 years
- Docker - 7 years
- Amazon Web Services (AWS) - 5 years
- PostgreSQL - 5 years
- Kubernetes - 1 year
Preferred Environment
Go, Amazon Web Services (AWS), Docker, MySQL, PostgreSQL, Blockchain, Microservices
The most amazing...
...thing I've implemented was the back end for TEE with DUKPT to process NFC transactions for mobile and POS.
Work Experience
Senior Software Engineer
2023 - 2026
Teranode Group
- Maintained a production token-indexing service (1Sat Ordinals, BSV-20/21) in Go, improving indexing throughput 10 to 40 times and cutting large-block indexing time from around 30 to 1.5 minutes (WhatsOnChain).
- Grew service ownership from one to four production services (token-service, token-mempool, woc-sockets V2, p2p-service).
- Built an AI-assisted development plugin and used it to implement a PostgreSQL datastore instead of Neo4j in 3 days, versus a 1+ month estimate, while improving indexing throughput 3.6 to 100 times.
Technologies: GoLand, gRPC, REST APIs, Neo4j, PostgreSQL, Bitcoin, Amazon OpenSearch, Prometheus, Grafana, GitHub, Jenkins, Unit Testing, Performance Testing, Functional Testing, Microservices, Back-end, APIs, Go
Senior Software Engineer
2022 - 2023
Monerium
- Integrated 3rd-party AML screening of blockchain addresses with notification.
- Refactored the platform to simplify 3rd-party applications management with a developer-facing REST API.
- Implemented multi-chain support and part of the cross-chain transaction feature.
- Implemented fixes and improvements in transaction flow, OAuth, etc.
- Implemented API automatic testing with Postman test scripts.
Technologies: Go, PostgreSQL, WebSockets, Docker, Kubernetes, Google Cloud Platform (GCP), Web3, REST APIs, Microservices, GitHub, APIs, Back-end
Senior Software Engineer
2020 - 2022
Divilo
- 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 (SNS), DocuSign, REST APIs, Microservices, GitHub, Amazon Simple Queue Service (SQS), Amazon EventBridge, Full-stack, Node.js, APIs, Back-end
Senior Software Engineer
2019 - 2020
Merj
- 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), Back-end, APIs
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, Back-end
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, Back-end
Full-stack Developer
2015 - 2017
Freelance
- Participated in several projects (such as Payever, points marketplace for CaixaBank, Mobillogix, and SoHo).
- Implemented employer management and social interactions in the back end and front end.
- Refactored the tracking system with Mixpanel, improving performance.
- Integrated products migration to eBay, Amazon MWS/Advertising, and Google Shopping.
- Created a developer-facing REST API for gift card sales.
- Completed the implementation of product delivery/stock and loan confirmations, helping deliver the project on time.
- Improved the development environment by splitting services into Docker containers.
- Contributed to the adoption of Agile methodologies.
Technologies: REST APIs, GitHub, Git, Backbone.js, Docker, Redis, MariaDB, Symfony 2, PHP, NoSQL, MySQL, Full-stack, APIs, Magento 2, PostgreSQL, JavaScript, Back-end
Senior Full-stack Developer | Scrum Master
2014 - 2015
Typeform
- 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
BeRepublic
- 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 Authorize.net.
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), Back-end, APIs
Full-stack Developer | Team Leader
2011 - 2012
Diprotech
- 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
Experience
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.
AndorraFreeMarket
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 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.
Chicplace
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 http://elcodi.io/.
Newpsel
https://github.com/dpcat237/newpsel-webI 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
https://github.com/PaymentSuite/paymentsuiteI 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.
Education
2008 - 2010
Bachelor's Degree in Computer Science
IES Carles Vallbona - Granollers, Spain
Skills
Libraries/APIs
REST APIs, JSON API, Vue, jQuery, Backbone.js, Redis Queue, Node.js
Tools
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 (SNS), CircleCI, Amazon Simple Queue Service (SQS), Amazon OpenSearch, Grafana
Languages
Go, SQL, Java, C, PHP, JavaScript, HTML, CSS, CoffeeScript, Sass, Bash
Paradigms
Unit Testing, Microservices, Functional Testing, Behavior-driven Development (BDD), Lambda Architecture
Storage
MySQL, Redis, Elasticsearch, MariaDB, PostgreSQL, Amazon DynamoDB, Amazon S3 (AWS S3), NoSQL, Neo4j
Frameworks
Symfony, Symfony 2, .NET, Selenium, gRPC, Silex, Electron, Laravel, Android SDK
Platforms
Linux, Docker, Magento, New Relic, Kubernetes, MacOS, Windows, Firebase, Magento 2, Amazon Web Services (AWS), AWS Lambda, Google Cloud Platform (GCP), Blockchain
Other
APIs, Back-end, Networks, WebSockets, Android Wear, Chrome Extensions, Serverless, DocuSign, Web3, Amazon EventBridge, Full-stack, Minimum Viable Product (MVP), Bitcoin, Prometheus, Performance Testing
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