Сергій

SERHII KAPLUN
Senior Full-stack Engineer (Node.js / NestJS / PostgreSQL / React)
Mail: [open contact info](look above in the "contact info" section)
LinkedIn: [open contact info](look above in the "contact info" section)
SUMMARY:
Senior Full-stack Engineer with 7+ years of commercial experience developing SaaS products, internal
platforms, and customer-facing web applications.
Strong in TypeScript, Node.js, NestJS, PostgreSQL, React and Next.js, with hands-on experience across
backend, database design, frontend, and production delivery.
Experienced in delivering features end-to-end, including authentication and RBAC, Stripe billing, AI
integrations, CI/CD, AWS deployment, and production support.
TECHNICAL SKILLS:
Backend: Node.js, NestJS, Express.js
Frontend: React, Next.js, TypeScript, TanStack Query, Zustand, Redux Toolkit, Tailwind CSS
Database & ORM: PostgreSQL, MongoDB, Prisma, Drizzle
Cloud & DevOps: AWS (ECS, EC2, RDS, S3), Docker, GitHub Actions, CI/CD
Other: REST API, WebSockets, GraphQL, JWT, Redis, NextAuth, Stripe
Testing: Jest, React Testing Library, Cypress
AI Engineering: OpenAI API, Prompt Engineering

PROFESSIONAL EXPERIENCE:
Senior Full-stack Engineer (Product Development) | March 2025 - June 2026
Hiring Platform SaaS (Full-stack)
● Developed a recruitment automation SaaS for managing vacancies, candidates, interview
workflows, and candidate evaluation.
● Implemented Stripe subscriptions, billing workflows, and plan-based quota logic.
● Built AI-powered candidate-to-vacancy matching using OpenAI embeddings.
● Designed a modular backend using NestJS, Prisma, and PostgreSQL.
● Developed calendar event management and global search across platform entities.
● Built an AI-powered assistant that provided contextual guidance on application workflows and
directed users to relevant platform pages based on their requests.
Tech: TypeScript, NestJS, Remix, Prisma, PostgreSQL, Stripe, OpenAI API.
Full-stack Engineer | ElifTech (Project-based) | April 2024 - January 2025
Soil Analysis CRM System (Full-stack)
● Developed full-stack functionality for a CRM supporting chemical analysis and environmental data
processing.
● Implemented backend logic for environmental data evaluation and mathematical calculations.
● Developed end-to-end validation schemas with Zod for secure and accurate laboratory data
uploads.
● Contributed to PostgreSQL schema design and wrote optimized queries using Drizzle ORM.
Tech: Next.js, Node.js, PostgreSQL, Drizzle, Zod.
Independent Projects & Professional Development | October 2023 - April 2024
● Updated full-stack expertise through independent projects using React, Next.js, Node.js, NestJS,
Prisma, and PostgreSQL.
● Completed technical assessments, communicated with prospective clients, and explored freelance
opportunities through Upwork.
Full-stack Engineer | NLT | December 2020 - May 2023
Administrative Dashboard for Multi-Service Platform (Frontend)
● Built interfaces for viewing and managing customer and transaction data.
● Implemented filtering, sorting, and pagination for data-heavy tables.
● Developed role-based access control with granular permissions for different user roles.
● Implemented two-factor authentication using QR codes.
● Collaborated within a six-person cross-functional team and integrated the frontend with
.NET-based backend APIs.
Tech: React, Redux Toolkit, TypeScript.
Cryptocurrency Platform (Full-stack)
● Developed a platform supporting cryptocurrency transactions with BTC, ETH, and USDT.
● Integrated MetaMask and WalletConnect for authentication and transaction workflows.
● Implemented a multi-level referral system with reward calculation logic.
Tech: React, Express.js, Redux, PostgreSQL, Docker.
Car Rental Management Dashboard (Frontend)
● Developed a React-based administrative dashboard for managing a car rental service.
● Built functionality for creating and editing fleet vehicles and managing vehicle-related information.
● Implemented an interactive timeline widget displaying vehicle availability, bookings, maintenance
periods, and current operational status.
● Integrated the frontend with backend APIs and an external authentication and authorization
service.
Tech: React, ReactN, TypeScript, Formik.

EARLIER EXPERIENCE:
Full-stack Developer | Valant | July 2020 - November 2020
● Worked with React, Vue.js, backend development, API integration, and bug fixing.
Front-end / Full-stack Developer | Digital Suits | May 2018 - May 2020
Music Events Booking Service (Frontend)
● Developed frontend functionality for a platform that allowed clients to book artists and musicians
for events.
Property Operations Platform (Frontend)
● Developed client-facing and administrative applications for managing property sales, purchase
requests, sellers, buyers, and quotes.
Housing and Tenant Management Service (Full-stack)
● Developed frontend and backend functionality for a platform supporting communication and issue
management between property owners and tenants.
Tech: React, Redux, Redux Thunk, TypeScript, Node.js, Express.js, Sequelize, Axios, Webpack.
Full-stack Developer | Innotech | October 2016 - May 2018
● Developed frontend interfaces and backend functionality using Ext JS, PHP, and MySQL.
EDUCATION:
Kharkiv Institute of Banking - Specialist Degree
LANGUAGES:
English: Upper-Intermediate (B2)