Ruslan K

Senior Fullstack Developer

Feb 2023 - Present • 3 yrs 5 mos

• Architected client-side data layer with React hooks, useMemo, and TanStack Query for AI-driven financial metrics, integrated WebSocket with cache invalidation that cut re-renders and API calls by 34%. • Designed streaming UI with incremental rendering for AI-generated responses, combined with client-side caching strategies that cut redundant API requests by 27%. • Built and optimized a high-load financial data grid handling 10000 to 50000 rows per session, applied virtualization and memoization techniques that improved Lighthouse performance score from 62 to 91. • Refactored Zepth Core module into a microfrontend architecture with TypeScript and Module Federation, which accelerated release cadence from monthly to weekly. • Extended TanStack Query with Server-Sent Events for real-time financial updates, with stale-while-revalidate and background refetch that cut stale data incidents by 18%. • Developed WBS-to-BIM integration mapping task entities to 3D model elements, synchronizing UI state with an external 3D viewer for selection, highlighting, and filtering, with manual cross-referencing time down by 31%. • Accelerated E2E test authoring 2.5x by introducing Claude Code into the Playwright workflow on GitLab CI/CD, which expanded critical financial flow coverage from 41% to 89%.

Fullstack Developer

Jan 2021 - Feb 2023 • 2 yrs 1 mo

• Migrated a rule-driven campaign and segmentation configurator for 200K+ DAU retention flows to Feature-Sliced Design (FSD), which cut TTM for promotional workflows by 22%. • Built centralized auth for internal and partner modules with Next.js, Zustand, and Keycloak, with unintended logouts down 47% and onboarding for new providers cut from 2 weeks to 3 days. • Designed AML and KYC form flows with Zod validation and persistent state recovery, with verification dropoff cut from 34% to 19%. • Implemented Next.js Middleware for cross-module auth and locale routing, which reduced unauthorized API hits by 36% and unified session handling across 4 partner integrations. • Resolved XSS, session handling, and data exposure vulnerabilities across frontend modules with Security Engineers, enabling external audit completion with zero critical findings. • Delivered a payment page with geo-aware methods and WebSocket-driven status and balance updates, with successful transaction completion up by 14%.

Fullstack Developer

Nov 2017 - Jan 2021 • 3 yrs 2 mos

• Developed a MUI-based UIKit with Storybook and independent CDN publishing, adopted across 6 product teams serving 2M+ MAU, with feature time-to-market down by 32%. • Improved Core Web Vitals for data-heavy account and reporting pages through CSR-to-SSR migration with Next.js, which cut initial page load time by 38%. • Migrated portfolio and account views from MobX to RTK Query with WebSocket sync, which cut stale-state support tickets by 41% and state-management boilerplate by 32%. • Implemented E2E testing with Playwright and integrated it into GitLab CI/CD pipelines, with critical user flow coverage reaching 97% and regression incidents down by 63%.