Open to opportunities

Sachin Kumar

@sachinkumar14

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Backend-focused full-stack developer building scalable, production-grade apps.

India

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What I'm looking for

I’m looking for a role where I can build secure, scalable backend systems and full-stack products—shipping REST APIs, microservices-ready architectures, caching and rate limiting, and real-time features with strong system design and performance.

I’m a backend-focused full-stack developer who builds scalable, production-grade applications with Node.js, Express.js, MongoDB, and Redis. I craft RESTful APIs, secure authentication/authorization (JWT, refresh rotation, sessions), and design microservices-ready architectures.

I enjoy high-concurrency problem solving—like preventing overselling with ACID transactions and reservation-based locking, plus Redis-backed TTL recovery using BullMQ workers. I also focus on reliability and security through idempotent APIs, fault-tolerant workflows, and multi-layer rate limiting.

From real-time messaging (Socket.IO, JWT via HTTP-only cookies, room-based presence) to e-commerce payments (Stripe) and media handling (Cloudinary), I ship features end-to-end with performance optimization, caching strategies, and web application security principles.

Experience

Work history, roles, and key accomplishments

Urban Stitch E-Commerce App

Urban Stitch

Mar 2026 - Apr 2026 (1 month)

Developed a full-stack e-commerce platform using MERN with JWT authentication and RBAC authorization. Integrated Stripe payment workflows and improved backend performance using Redis caching, following production-ready modular architecture practices.

React MongoDB Redis Stripe Cloudinary JWT RBAC

Chat Sync Real-Time Messaging

Chat Sync

Feb 2026 - Mar 2026 (1 month)

Built a real-time messaging platform using Socket.IO with WebSocket-based delivery and JWT authentication via HTTP-only cookies. Designed scalable room-based architecture with presence tracking, media messaging via Cloudinary, and optimistic UI updates for responsive chat.

MongoDB Socket.IO WebSockets React Zustand JWT Cloudinary

E-Commerce Inventory Service

Jan 2026 - Feb 2026 (1 month)

Built a high-concurrency inventory microservice to prevent overselling using ACID transactions and reservation-based locking. Implemented Redis-backed TTL reservations with BullMQ workers for automatic recovery and consistency, along with idempotent APIs for safe retries.

MongoDB Redis BullMQ Microservices Architecture Distributed Systems

Secure Authentication Service

Jan 2026 - Jan 2026 (0 months)

Engineered a secure authentication backend with JWT, refresh token rotation, and Redis-based token blacklisting. Added multi-layer rate limiting (IP/login/user) to mitigate brute-force attacks and implemented an OTP-based password reset with account lock.

MongoDB Redis JWT Refresh Token Rotation Rate Limits Security Best Practices