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Sergey Royz
Verified Expert in Engineering
Software Developer
Prague, Czech Republic
Toptal member since January 13, 2015
Bio
Sergey is a highly skilled software engineer with over 15 years of experience in development and architecture design. He worked for fintech startups, medical companies, the travel industry, and home automation. He has a strong understanding of OOP and FP concepts and experience with applying design patterns. Sergey prides himself on his ability to create robust and maintainable code.
Portfolio
Swipelux OU
Web3, Spring Boot, Docker, Kubernetes, PostgreSQL, Blockchain, Ethereum...
Toptal Clients
Koa, Node.js, Spring Boot, Docker, Amazon Web Services (AWS), SAML-auth, React...
Absa
Apache Spark, Plotly, Python 3, Docker, Rancher, SQL, Jira, JavaScript...
Experience
- JavaScript - 12 years
- Java - 9 years
- SQL - 9 years
- Python - 7 years
- Hibernate - 5 years
- Spring MVC - 4 years
- Spring - 4 years
- AngularJS - 1 year
Preferred Environment
MacOS, Vim Text Editor, Git, IntelliJ IDEA, Visual Studio Code (VS Code), Sublime Text 3, AI Agents, Large Language Models (LLMs), TypeScript, Generative Artificial Intelligence (GenAI), Prompt Engineering
The most amazing...
...thing I've built was a fully working fiat to a crypto payment gateway, including integrations with an exchange, KYC provider, and multiple blockchains.
Work Experience
CTO | Co-founder | Full-stack Engineer
2020 - PRESENT
Swipelux OU
- Built a prototype from scratch, a widget allowing processing payment cards, an integration with a Know Your Customer (KYC) provider, and an integration with a crypto exchange.
- Led technical communication with investors during the pre-seed round of investments.
- Spearheaded the development process, managing a team of 8–10 people and negotiating with business and development.
Technologies: Web3, Spring Boot, Docker, Kubernetes, PostgreSQL, Blockchain, Ethereum, Smart Contracts, Amazon Web Services (AWS), Cryptocurrency, Bots, Decentralized Finance (DeFi), Team Leadership, Leadership, Payment APIs, Technical Leadership, Architecture, API Integration, REST APIs, Data Engineering, Open Source, Cloud, API Documentation, Web App Development, Full-stack, Full-stack Development, DevOps, GitHub, AWS Lambda, React, Material UI, CSS3, Flutter, Data Visualization, Database Modeling, Automation Scripting, Scripting, Admin Panels, Automation, Vue 2, Airtable, Minimum Viable Product (MVP), Node.js
Senior Full-stack Engineer
2018 - PRESENT
Toptal Clients
- Automated data flow with a Selenium WebDriver and UI Automator.
- Implemented many integrations of IoT devices via REST API, MQTT, and Apache Pulsar.
- Implemented Security Assertion Markup Language (SAML) integration into an existing solution.
- Applied a user-management console with React and Koa.js.
- Developed multiple microservices and split monolith app.
- Developed firmware update solution for IoT devices using AWS infrastructure (S3, SNS, SQS, MQTT).
Technologies: Koa, Node.js, Spring Boot, Docker, Amazon Web Services (AWS), SAML-auth, React, Redux, Python 3, SQL, JavaScript, Spring MVC, Spring Security, Code Review, Source Code Review, Algorithms, ESP32, Arduino, CSS, HTML, Web Scraping, APIs, Bots, Architecture, API Integration, REST APIs, Data Engineering, Open Source, Data Science, Cloud, API Documentation, Web App Development, Full-stack, Full-stack Development, DevOps, GitHub, AWS Lambda, Dashboards, Material UI, CSS3, Responsive Web Design (RWD), Internet of Things (IoT), Data Visualization, Database Modeling, Automation Scripting, Scripting, Admin Panels, Automation, Vue 2, Airtable, Minimum Viable Product (MVP)
Data Science Engineer
2020 - 2021
Absa
- Implemented rules for a rule-based anti-fraud detection engine.
- Managed, implemented, and deployed a BI dashboard POC with Plotly.
- Provided training on the usage of internal deployment automation tools such as Rancher and Subatomic.
Technologies: Apache Spark, Plotly, Python 3, Docker, Rancher, SQL, Jira, JavaScript, Code Review, Source Code Review, Interviewing, Flyway, HTML, APIs, Payment APIs, Architecture, API Integration, REST APIs, Data Engineering, Data Science, Cloud, API Documentation, GraphQL, Full-stack, Full-stack Development, DevOps, GitHub, React, Dashboards, Data Visualization, Database Modeling, Automation Scripting, Scripting, Admin Panels, Google Sheets, Automation, Vue 2
Senior Software Engineer
2018 - 2019
Omio (formerly Goeuro)
- Implemented several integrations with ferry ticket providers.
- Dockerized and deployed microservices to Kubernetes.
- Redesigned the flow of the integration development to be more modular and testable.
Technologies: Spring Boot, SOAP, Kubernetes, Docker, Jira, JavaScript, Spring MVC, Code Review, Source Code Review, HTML, APIs, Technical Leadership, Architecture, API Integration, REST APIs, Open Source, Cloud, API Documentation, GraphQL, Web App Development, Full-stack, Full-stack Development, DevOps, GitHub, React, Database Modeling, Automation Scripting, Scripting, Admin Panels, Google Sheets, Automation
SAML Developer
2017 - 2018
Radix Health
- Developed a SAML integration to an existing Spring-based application allowing authorization to users via a third-party identity provider (IdP).
- Implemented integration with Shibboleth using PHP.
- Effectuated a user and key management admin console with Koa.js and React.
Technologies: Spring Security, Java, SAML, Spring, SAML-auth, PingFederate, API Integration, REST APIs, Cloud, API Documentation, Full-stack, Full-stack Development, GitHub, Database Modeling, Automation
Senior Software Engineer
2017 - 2018
Cisco
- Extracted microservices from the monolithic architecture.
- Dockerized microservices, wired them together with Docker Swarm for the PoC.
- Worked on migrating the microservice infrastructure to AWS.
- Prepared data for cognitive threat analysis of the machine learning models.
Technologies: Spring Boot, Amazon Web Services (AWS), Docker, Machine Learning, Terraform, Python, SQL, Jira, JavaScript, Spring MVC, Code Review, Source Code Review, HTML, APIs, Architecture, API Integration, REST APIs, Data Engineering, Cloud, API Documentation, Web App Development, Full-stack, Full-stack Development, GitHub, Database Modeling, Automation Scripting, Scripting
Senior Software Engineer
2016 - 2016
Hewlett Packard Enterprise
- Maintained current solution of operations and log analysis.
- Implemented a Slack chatbot for automating the development pipeline.
- Worked on dockerization of an existing solution for operations analytics.
Technologies: Docker, Spring Boot, CoffeeScript, Spring MVC, APIs, API Integration, REST APIs, Cloud, API Documentation, GitHub, Database Modeling
Lead Software Engineer
2012 - 2016
Instabank
- Created architecture and developed a back end for upupapp.com.
- Implemented various integrations with banking systems.
- Developed integrations with internal banking systems.
- Applied account status and statement report module.
Technologies: MongoDB, PostgreSQL, Scala, Play Framework, Django, Python, Hibernate, Spring, Java, SQL, Jira, JavaScript, Spring MVC, Code Review, Source Code Review, Interviewing, Web Scraping, APIs, Technical Leadership, Architecture, API Integration, REST APIs, Cloud, Database Modeling, Scripting
Lead Software Engineer
2011 - 2012
iDaMobile
- Implemented mobile banking apps for five banks in Russia.
- Programmed a back end for a mobile banking solution.
- Integrated a mobile banking solution into a bank's infrastructure.
Technologies: Python, PostgreSQL, Android, Jakarta EE (Java EE or J2EE), SQL, JavaScript, Spring MVC, Code Review, Source Code Review, Interviewing, Web Scraping, APIs, Technical Leadership, Architecture, API Integration, REST APIs, Cloud, GitHub, Scripting
Lead Software Engineer
2010 - 2011
NetCracker
- Performed business analysis of the projects at customer's site in Malaysia.
- Implemented a J2ME App for Blackberry and integrated it with the platform.
- Architected and implemented a high-performance distributed management system of network devices.
Technologies: SOAP, Jakarta EE (Java EE or J2EE), J2ME, SQL, Spring MVC, Oracle, Code Review, Source Code Review, Interviewing, APIs, Architecture, API Integration, REST APIs, Scripting
Software Engineer
2009 - 2010
Yandex
- Supported integration and deployment.
- Improved internal analytical tools.
- Integrated an internal data mining tool into the project.
Technologies: Swing, MySQL, Jakarta EE (Java EE or J2EE), SQL, Spring MVC, API Integration, REST APIs, GitHub
Senior J2EE Developer
2005 - 2009
NetCracker
- Developed a plugin for Eclipse for the graphical merge of business process diagrams.
- Performed platform customization for the customer's needs.
- Implemented LDAP integration.
- Provided product support at a customer's site in Belgium.
- Worked as Java instructor in a learning center.
Technologies: Web Services, Oracle PL/SQL, Jakarta EE (Java EE or J2EE), SQL, Spring MVC, Oracle, API Integration, REST APIs
Experience
Rapid Card2Card Transfer Service
A service that allows rapid card-2-card transfers by providing integration with a third-party payment gateway. The service is a peer-to-peer payment solution, with no registration needed.
I developed the project from the early stages to production.
I developed the project from the early stages to production.
Kwenda: Tourist City Guide for Android
Kwenda is a comprehensive mobile city guide application designed specifically for tourists exploring unfamiliar urban environments. The app transforms the tourist experience by providing an intelligent, interactive platform for discovering and navigating points of interest across cities.
At its core, Kwenda serves as a digital tour companion that helps users discover attractions, restaurants, historical sites, parks, museums, and other notable locations within a city. The application aggregates point of interest (POI) data and presents it through an intuitive, map-based interface that makes urban exploration straightforward and enjoyable.
At its core, Kwenda serves as a digital tour companion that helps users discover attractions, restaurants, historical sites, parks, museums, and other notable locations within a city. The application aggregates point of interest (POI) data and presents it through an intuitive, map-based interface that makes urban exploration straightforward and enjoyable.
Clustering Large Sets of Objects on The Map
I implemented an algorithm for building static clusters of geolocations and pre-calculating them for different zoom levels. I integrated it with a mobile banking app, and it works in production, perfectly handling more than 50,000 objects.
Flat-sharing Platform: Coliver
A platform for searching for future flatmates for sharing an apartment rental in big cities. I was a full-stack developer and implemented an MVP from scratch. The back end was implemented in Java/Spring Boot, the front end was implemented with Vue, and the service was run on Kubernetes.
AI Administrator for a Nail Salon
An intelligent conversational AI agent that serves as a virtual administrator for a nail salon, handling customer inquiries and appointment bookings autonomously through Instagram Direct Messages.
The bot engages customers in natural conversations, answers questions about services, checks real-time availability, and completes booking transactions without human intervention.
It operates 24/7, providing instant responses and managing the entire customer journey from initial inquiry to confirmed appointment.
The bot engages customers in natural conversations, answers questions about services, checks real-time availability, and completes booking transactions without human intervention.
It operates 24/7, providing instant responses and managing the entire customer journey from initial inquiry to confirmed appointment.
Zempo: Marathon Runner's AI Coach
An AI-powered coaching bot accessible via Telegram that creates personalized marathon training plans. Integrates with Strava to analyze running history and performance data, uses voice interactions through LiveKit, and employs AI agent tools to provide adaptive, data-driven training recommendations tailored to each runner's progress.
Quest Connect
QuestConnect is a social facilitation platform that transforms party networking by using AI to generate personalized icebreaker stories. The system collects responses to open-ended questions from event participants, processes them through AI to create engaging conversational prompts, and distributes these stories to attendees before the event.
Education
2006 - 2009
Master's Degree in Computer and Information Science
Moscow Institute of Physics and Technology (State University) - Moscow, Russia
2003 - 2006
Bachelor's Degree in Applied Mathematics and Physics
Moscow Institute of Physics and Technology (State University) - Moscow, Russia
Certifications
JANUARY 2021 - PRESENT
CSMM.103x: Robotics
edX
SEPTEMBER 2020 - PRESENT
Certified Rancher Operator: Level One
Rancher Labs
AUGUST 2019 - PRESENT
AI for Everyone
Coursera
JANUARY 2014 - PRESENT
Functional Programming Principles in Scala
Coursera
Skills
Libraries/APIs
React, Node.js, REST APIs, Vue, Vue 2, jQuery, PyTorch
Tools
GitHub, Vim Text Editor, Jira, Git, Flyway, Google Sheets, IntelliJ IDEA, Sublime Text 3, Terraform, Plotly
Languages
Java, JavaScript, HTML, Python, CSS, SQL, CSS3, TypeScript, HTML5, Bash Script, Scala, CoffeeScript, Python 3, SAML, GraphQL
Paradigms
Automation, Functional Programming, Concurrent Programming, Design Patterns, Object-oriented Programming (OOP), DevOps, Responsive Web Design (RWD), REST
Storage
Database Modeling, PostgreSQL, MongoDB, Oracle PL/SQL, MySQL, PingFederate
Frameworks
Flutter, AngularJS, Spring Security, Spring MVC, Hibernate, Spring, Material UI, Swing, Play Framework, Django, Spring Boot, Koa, Redux, Apache Spark, Agentic Frameworks
Platforms
Android, Kubernetes, Blockchain, AWS Lambda, Jakarta EE (Java EE or J2EE), J2ME, Oracle, Visual Studio Code (VS Code), Docker, Amazon Web Services (AWS), Rancher, Arduino, Ethereum
Other
Code Review, Source Code Review, Web Scraping, APIs, Bots, Architecture, API Integration, Data Engineering, Web App Development, Full-stack, Full-stack Development, Automation Scripting, Scripting, Airtable, AI Agents, Minimum Viable Product (MVP), Generative Artificial Intelligence (GenAI), Prompt Engineering, Machine Learning, Interviewing, Cryptocurrency, Decentralized Finance (DeFi), Technical Leadership, Open Source, Cloud, API Documentation, Dashboards, Internet of Things (IoT), Bluetooth, Hardware, Data Visualization, Admin Panels, Large Language Models (LLMs), Web Services, SOAP, Robot Operating System (ROS), Data Science, SAML-auth, Algorithms, ESP32, Web3, Smart Contracts, Scraping, Team Leadership, Leadership, Payment APIs, OpenAI, Tree Structures, LangChain, Agentic AI, FastAPI, Vibe Coding
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