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Sergii – Angular, Node.js, JavaScript, experts in Lemon.io

Sergii

From United Kingdom (UTC+1)

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Full-stack Web DeveloperSenior
Tech lead
CTO
Engineering Manager
17 years of commercial experience
Asset management
Aviation
Banking
Blockchain
Business intelligence
Cryptocurrency
Fintech
Logistics
Transportation
Trade
Communication tools
Enterprise software
Mobile apps
Platforms
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Sergii – Angular, Node.js, JavaScript

Sergii is a skilled engineer and CTO with over 15 years of hands-on experience in front-end and back-end software development, primarily in the financial sector. He has also worked in the gambling, telecommunications, and aviation industries. Sergii has experience building systems from scratch and has worked with major parcel delivery services in the UK. Previously an AI lead, he led his company into receiving 50K$ from Microsoft as an AI startup. With a readiness for new challenges, Sergii will be a perfect addition to your team.

Main technologies
Angular
12 years
Node.js
12 years
JavaScript
15 years
Typescript
12 years
Additional skills
Firebase
React Native
MongoDB
GCP
MySQL
Highcharts
Microsoft Azure
Product management
OpenAPI
Cloud Architecture
GraphQL
Apollo GraphQL
Blockchain
Crypto
Jenkins
Database design
PHP
React
OpenAI
Azure DevOps
Ready to start
ASAP
Direct hire
Potentially possible
Ready to get matched with vetted developers fast?
Let’s get started today!

Experience Highlights

Principal Technologist
Mar 2020 - Feb 20254 years 11 months
Project Overview

A modular technology and experience platform, application toolkits and integration layers that allow providing private banking platform with great UX and rollout for new private office or bank just in a few weeks. Functionality includes wealth management and crypto investments. It is an MXDP set of applications, hosted on Azure - Java microservices backend, Flutter modular mobile app, and Angular + React web microfrontend applications based on a cutting-edge module federation approach.

Within this project Sergii built and coached a team of engineers from various tech stacks (Java, Angular, React, Node) to become AI developers, enabling them to develop solutions using Python, Azure OpenAI, Azure AI Search, Azure Document Intelligence, and FAISS. The team successfully built an AI-powered financial advisor chat for investment fund document analysis and AI-driven health protocols on Azure Databricks to assist Health Coaches within our longevity startup.

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Responsibilities:
  • Built and led a 20-member engineering team, including 8 direct reports (experts in Angular, React, Java, Node, Selenium, Azure, Kubernetes), ensuring the necessary resources and structure for scaling the system, streamlining feature delivery, and enhancing client satisfaction through faster, more reliable releases.
  • Set up an org-wide mentorship program. Mentored engineers with 40% achieving promotion in the next performance review cycle, which boosted retention and morale, creating a stronger, more capable engineering workforce to drive long-term business success.
  • Developed a comprehensive knowledge-sharing repository with video recordings and newcomer onboarding check-lists, reducing time-to-productivity by over 60% and improving the retention of new hires.
  • Reduced front-end deployment time by over 60x through a ”build once, deploy anywhere” strategy (with Docker registry), cutting operational costs and ensuring rapid, efficient responses to changing business demands.
  • Enhanced test coverage to 60-95% (Jest, JUnit) by integrating automatic coverage checks at the PR stage (Sonar, Jenkins), resulting in positive customer feedback on the improved consistency and quality of releases.
  • Boosted developer productivity by 30%, as reflected in team velocity charts, by leveraging AI toolset, SCRUM process improvements, and JIRA automation, directly impacting product delivery speed and engineering efficiency.
  • Spearheaded cross-organizational engineering initiatives to ensure ISO 27001, GDPR, and HIPAA compliance for AI products (on Python, Databricks, OpenAI) by collaborating with legal, security, and product teams to implement secure data handling, access controls, audit logging, and privacy-preserving ML techniques, enabling market expansion.
Project Tech stack:
Angular
Typescript
Webpack
Highcharts
Angular Material
Cloud Architecture
Product management
Database design
OpenAPI
Apollo GraphQL
GraphQL
Crypto
Blockchain
Microsoft Azure
Jenkins
OpenAI
OpenAI API
Azure DevOps
Lead Full Stack Developer
Jul 2019 - Apr 20208 months
Project Overview

A platform that allows transactions in the private securities market to be conducted digitally while meeting the current regulatory record-keeping requirements. Underpinning the business is an enterprise-private permissioned blockchain platform (distributed ledger). It creates a unique opportunity to implement a new capital raising and trading infrastructure that provides a trusted, secure source of information at a materially lower cost to use while being compliant with very strict regulatory requirements.

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Responsibilities:
  • Set up the processes and multifunctional full-stack team collaboration;
  • Developed new features on both Angular front-end and NodeJS backend with MongoDB;
  • Refactored existing functionality, and participated in CI/CD setup, and hands-on development.
  • Facilitated Scrum of Scrums meetings, improving project visibility and coordination across 3 teams, which led to a 20% improvement in sprint planning accuracy and a 50% increase in on-time delivery for cross-functional projects.
  • Implemented a technical debt resolution process, reducing the tech debt backlog by 70% within three months.
  • Established automated static code analysis pipelines, allowing code reviewers to focus on security and architectural improvements. This reduced the average time spent for PR reviews by up to 50% and increased the relevance and value of each comment.
Project Tech stack:
Angular
Typescript
Node.js
MongoDB
Technical Lead
Jul 2018 - Jul 20191 year
Project Overview

Complex solutions for the end-users and management of the largest parcel delivery company in the United Kingdom. One of them was a smartphone application built with React Native, Firebase, and NodeJS backend hosted on Google Cloud Platform and using all available Firebase functionality (including GC Functions, Firestore Database, etc.). The app reached 1 mln. active users in a few weeks and was highly rated on Google Play and AppStore.

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Responsibilities:
  • Led a high-performing Scrum team of 5 full-stack developers (React Native, React, GCP, Firebase), 2 manual QA engineers, and an automation engineer, delivering complex solutions for one of the UK’s largest parcel delivery companies.
  • The app achieved rapid user adoption, reaching 1 million successful registrations within weeks and earning high ratings of 4.9 on Google Play and App Store.
  • Innovated and implemented an automated solution for generating visually appealing, cross-client-compatible email templates, increasing template creation speed by 5x and ensuring consistent rendering across all major email clients.
Project Tech stack:
JavaScript
React
React Native
GCP
Node.js
Lead JavaScript Developer
Jun 2014 - Jun 20184 years
Project Overview

These were both projects from scratch, one of the most massive and exciting projects in the company's portfolio. The team used a wide array of technologies: we were hacking and creating infrastructure mainly on AngularJS / Angular 2, Node.js for CLI tools and backend services, bower for dependency management, plus a few build tools of choice for various sub-products, based on the project's needs. During this project, the team faced many challenges, they analyzed existing functionality, and transformed & adapted it into something great using the latest stack of Web technologies.

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Responsibilities:
  • Led the development of the PCI-DSS compliant SDK for seamless and secure payment integration with 100 M EUR monthly in transactions.
  • Innovated and implemented a visual editor for the rules engine, reducing setup time for new rules by 90% and increasing ease of use, leading to a 15% boost in operational efficiency for payment system processes.
  • Developed a performant Excel-like table on AngularJS for transaction management, featuring flexible columns, filters, inline editing, and efficient lazy-loading for seamless interaction with over 5000 interactive elements within a single page.
Project Tech stack:
Angular JS
Angular
Node.js
JavaScript
TeamCity
Full stack developer
May 2012 - Jun 20142 years
Project Overview

Web App for pilots of private aircraft that allows building a fully integrated flight planning, filing, dispatch, crew briefings, tracking, and more. It was built on PHP, on the front end the team started with an app on AngularJS and TypeScript, when it even wasn't officially released yet (was in beta).

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Responsibilities:
  • Optimized processing of binary weather forecast METARS data, achieving a significant speedup from 14 hours to 35 minutes by rewriting the algorithm in C and implementing efficient batch imports to MySQL.
  • Led a successful migration from SVN to Git, improving conflict resolution time by 20-40% and accelerating development (PHP, RoR, React, Angular, TypeScript) and debugging processes by 30%, resulting in smoother version control and enhanced team productivity.
Project Tech stack:
PHP
Angular JS
Typescript
MySQL

Education

2012
Computer Science
Master's

Languages

Russian
Advanced
Ukrainian
Advanced
English
Advanced

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