4+
Years Experience
Backend-heavy product delivery
SYSTEM ONLINE // Available for Work
MERN Stack Developer
BUILDING BOLD PRODUCTS KUNAL SINGH.
I build backend-heavy web products that stay fast, stable, and easy to evolve.
Across four years, I have shipped full-stack systems spanning commerce, CRM, logistics, and conversational automation.
Node.jsExpress.jsTypeScriptReact.jsNext.jsMySQLMongoDBPostgreSQLAWS EC2AWS S3Socket.ioPayment GatewaysMQTT
6
Products Shipped
Case studies across multiple domains
9.33
GPA
B.Sc. IT, University of Mumbai
10+
Integrations Built
PayU, Razorpay, MQTT, Zoom, Facebook, WhatsApp, IVR...
KS
IDENTITY_PACKET
Full-stack execution with product instincts.
PROFILE_TRACE
I am a MERN stack developer based in Thane, Mumbai, focused on shipping product experiences that balance frontend polish with strong backend architecture.
My work usually sits close to the business: payments, CRM automation, workflow systems, real-time communication, and operational tooling that teams rely on every day.
I enjoy owning the full delivery path from API and database design through UI implementation, deployment, and production hardening.
SELECTED_LOGS
Case studies built around backend depth, real integrations, operational workflows, and production surfaces that stay clear under pressure.
TOTAL_ITERATIONS: 7
Sublime TechnoCorpLOG_01
Morix – Digital Signage Platform
A cloud-based digital signage SaaS with a multi-tier distribution model, split payment settlements, full media lifecycle management, and real-time device sync over MQTT — backed by a PostgreSQL database layer with triggers, functions, and stored procedures for business-critical operations.
Node.jsExpress.jsTypeScriptPostgreSQLMongoDBMQTTPayUREST APIs
- Architected the full backend for a multi-tier SaaS — Admin, Distributor, and Sub-Distributor with scoped access control
- Designed the PostgreSQL schema with triggers, stored procedures, and database functions to handle business-critical workflows at the data layer
- Built inventory, license, lead, and order management modules across the distribution layer
- Integrated PayU Payment Gateway with split payment logic to automatically divide commission and actual amount across the distribution hierarchy
Sublime TechnoCorpLOG_02
MK Gare Jewelers – Jewellery E-Commerce Platform
A full-stack jewellery e-commerce platform with static page generation, real-time metal price-driven product pricing, a making charge discount engine, inventory-aware order management, and PayU checkout with coupon support.
Next.jsNode.jsExpress.jsPostgreSQL
- Built a jewellery e-commerce platform with Next.js static page generation for SEO-optimized product and category pages
- Designed a dynamic pricing engine that calculates product prices in real time based on live gold and silver metal rates — keeping prices consistent across the entire application
Sublime TechnoCorpLOG_03
Auction-Based E-Commerce Platform
A backend-heavy commerce platform combining time-bound auction flows, Razorpay payments, and Zoom-powered live sessions — letting sellers present items in real time while buyers bid and transact in the same flow.
Node.jsExpress.jsRazorpayZoom SDK
- Designed and shipped the full auction lifecycle API — open, active bidding, close, winner resolution, and payment trigger
- Handled bid concurrency with server-side validation to resolve simultaneous bids at the same price point
Sublime TechnoCorpLOG_04
CRM System
A lead and campaign operations system ingesting 500+ daily leads from five channels — Facebook, WhatsApp, IVR, IndiaMart, and Justdial — into a unified pipeline with automated assignment and follow-up workflows.
Node.jsExpress.jsFacebook SDKWhatsApp API
- Built a unified lead ingestion pipeline handling 500+ daily leads from five sources — Facebook, WhatsApp, IVR, IndiaMart, and Justdial
- Designed a normalisation layer to deduplicate leads across channels by matching on phone number and email, preventing the same prospect from appearing multiple times in the pipeline
Sublime TechnoCorpLOG_05
Freight Forwarding Management System
A full-stack management platform for a freight forwarding business covering quotation generation, job tracking across air, sea, and land shipments, multi-currency accounting, and document management in one operational system.
Next.jsNode.jsExpress.jsMySQL
- Owned full-stack delivery across quotation, job tracking, accounting, and document management modules
- Built a quotation engine that generated freight estimates based on shipment mode, origin, destination, weight, and volume
PersonalLOG_06
Automated Marketing Chatbot
A personal project — a visual workflow-driven chatbot builder for lead capture and automated engagement, combining a React Flow node editor, real-time Socket.io communication, and MongoDB-persisted flow execution.
Next.jsReact FlowSocket.ioMongoDB
- Designed the workflow data model — nodes and edges stored as a graph in MongoDB, each node carrying a type, prompt, and conditional routing config
- Built the React Flow visual editor for creating and modifying chatbot flows without writing code
PersonalLOG_07
Video Transcoder
A personal project — a browser-based video transcoding tool that accepts up to three video uploads and returns a single ZIP file containing each video re-encoded at 360p, 720p, and 1080p resolutions, powered by a server-side FFmpeg pipeline exposed over a REST API.
Node.jsExpress.jsFFmpegMulter
- Built the REST API endpoint to accept up to three video file uploads via multipart form-data using Multer
- Implemented the server-side FFmpeg transcoding pipeline to re-encode each uploaded video at 360p, 720p, and 1080p resolutions
CORE_LOGIC // DESIGN_PATTERNS
01
Split payment atomicity
Constraint
Each order must split revenue across three tiers — vendor, distributor, sub-distributor — without any tier missing their cut if a failure happens mid-transaction.
Rejected Path
Calculate splits in the API layer and fire three separate DB writes.
What I Did
Used a PostgreSQL stored procedure so the entire split executes as one atomic transaction. A failure at any step rolls back the full operation — no partial payouts.
- PostgreSQL
ACID for payment splits — one stored procedure rolls back the entire split if any step fails; no partial payouts across tiers.
- PayU
Split API at checkout enforces vendor / distributor / sub-distributor shares per order instead of reconciling in a batch job later.
02
Real-time device sync over MQTT
Constraint
Playlist updates published on the cloud must appear on physical signage screens within seconds, for any fleet size.
Rejected Path
Devices poll the API every N seconds for new playlists.
What I Did
Devices subscribe to an MQTT topic. The server publishes once; all subscribed devices receive the update instantly regardless of fleet size, with no polling overhead.
- MQTT
Sub-second device push — chosen over HTTP polling so fleet size does not add lag between publish and screen.
03
Offline screen reconciliation
Constraint
A signage device can be offline for hours and must resume the correct scheduled playlist on reconnect — not just the latest one.
Rejected Path
On reconnect, push the most recently published playlist.
What I Did
Device sends its last-known schedule timestamp on reconnect. The server evaluates which playlist should be active at that timestamp and pushes exactly that — preserving scheduled transitions that happened while offline.
- Edge + API
Reconnect sends last-known schedule timestamp; server resolves which playlist was active at that instant — not the latest publish the device never saw.
- MQTT
Correct playlist is pushed over the same pub/sub path as live updates once reconciliation completes.
04
Live pricing on statically generated pages
Constraint
Jewellery product pages must be statically generated for SEO, but prices float with live gold and silver market rates.
Rejected Path
Store prices in the DB and regenerate static pages when rates change.
What I Did
Separated static content (product details, images, categories — generated at build time) from dynamic pricing (always resolved from a live rate API at request time via client-side hydration).
- Next.js
SSG shell for crawlable product pages; metal and making-charge numbers hydrate after load so listed prices always track live rates.
- REST APIs
Every price read hits the rate-backed API at request time — no stale amounts baked into the static HTML.
05
Auction bid concurrency
Constraint
Two bidders can place the same bid amount at the exact same millisecond. Only one can win.
Rejected Path
Accept bids in the order they arrive at the API.
What I Did
Used optimistic locking at the DB write layer — a bid is accepted only if the incoming amount is strictly greater than the current highest bid at commit time. Simultaneous equal bids produce a deterministic rejection with a clear retry path.
- PostgreSQL
Optimistic locking at commit time — equal simultaneous bids lose deterministically unless the amount strictly beats the stored high bid, with a clear retry path.
TECHNICAL_ARSENAL
Backend Engineering
Building resilient APIs, business logic, and integration-heavy systems that support real product operations.
Node.js
Express.js
REST APIs
Socket.io
Frontend Development
Crafting responsive interfaces with modern React patterns and product-focused interaction design.
React.js
Next.js
React Flow
TypeScript
Databases
Designing and working with data models that support speed, clarity, and operational reliability.
MySQL
MongoDB
PostgreSQL
Cloud & Deployment
Shipping production-ready applications with dependable infrastructure and hosting workflows.
AWS EC2
AWS S3
SSL & Hosting
Deployment Ops
Languages
Using the right language for product engineering, systems thinking, and implementation depth.
JavaScript
TypeScript
C
C++
EXPERIENCE_HISTORY
May 2022 - Present
MERN Stack Developer
Sublime TechnoCorp
- Architected and shipped 5+ full-stack products across e-commerce, CRM, digital signage SaaS, and logistics — owning backend design, API development, and frontend delivery end-to-end.
- Designed production-grade REST APIs and database schemas across PostgreSQL, MySQL, and MongoDB, leveraging stored procedures, triggers, and database functions for business-critical workflows.
- Integrated payment gateways (PayU, Razorpay) with split-payment logic, coupon validation, and real-time pricing engines driven by live market data.
- Built multi-channel integrations across Facebook Business SDK, WhatsApp API, IVR, IndiaMART, JustDial, MQTT, and Zoom Video SDK for automation and real-time communication.
- Managed end-to-end production infrastructure — Ubuntu VPS provisioning, SSL certification, AWS EC2/S3 deployment, and CI/CD pipelines via GitHub Actions.
EDUCATION_CERT
B.Sc. IT
University of Mumbai
Built a strong academic foundation in software development, data handling, and applied computing.
GPA 9.33/10
HSC
Gandhi Nagar Public School, CBSE
SSC
Gandhi Nagar Public School, CBSE
LET'S
SYNC.
Open to product engineering roles and contract work — remote or on-site — where backend reliability and thoughtful frontend execution both matter.