Arsenii Golubiatnikov

Full-Stack Developer Early-stage Product

Contributed to the development of an early-stage, multi-tenant SaaS platform in the education and children's activities domain, working across the full product lifecycle from MVP to production-ready features. Key contributions: Led development of core full-stack features for a scalable SaaS application Built and maintained complex user flows around bookings, customers, and group management Implemented secure authentication and role-based access control Contributed to backend services, API design, and data modelling Integrated third-party services including payments, notifications, and external calendars Collaborated on performance optimisation, reliability, and deployment processes Worked closely with product stakeholders to deliver features aligned with business goals

Designed and implemented an FSD-based SPA architecture (120+ modules), ensuring scalability and maintainability. Migrated the project to React 18 + Vite, reducing dev-server startup time from 12s to 4s and improving LCP by 38% in production. Built a drag-and-drop scenario builder using React Flow. Developed a bulk email campaign module. Integrated Facebook and amoCRM SDKs, increasing MAU from 1.2k to 4.7k within one quarter. Introduced Storybook and React Testing Library, reaching ~85% UI test coverage. Tech stack: React 18, Vite, TypeScript, Redux Toolkit / RTK Query, React Flow, Material UI, Storybook

Key contributions: Participated in the migration of a monolithic frontend to a Next.js-based FSD architecture, improving TTI from 3.8s to 2.1s. Implemented a WebSocket-based chat with JWT authorization, supporting 300+ concurrent consultants. Built internal admin dashboards using Recharts and MUI, reducing manual reporting by ~4 hours per week. Integrated automated content generation using the OpenAI API, reducing consultation preparation time from 10 minutes to ~30 seconds. Improved MFA login and registration flows, increasing registration conversion by 18%. Tech stack: Next.js, React 18, TypeScript, Redux Toolkit, WebSocket, Recharts, styled-components, MUI, Axios, ESLint