Hi, I'm Bablu Kumar Singh
Most of what I build lives on the backend — APIs, database schemas, the occasional queue when things need to run async — with a multi-tenant SaaS platform (ROI Spectrum) as the biggest thing I've shipped so far.
Bablu Kumar Singh
Software Engineer
Noida, UP, India
Technical Expertise
Grouped by where it actually gets used — backend, data, infra, and the frontend/mobile side.
Backend Engineering
- Node.js
- Express.js
- REST APIs
- GraphQL
- Microservices
- RBAC Security
Databases & Cache
- PostgreSQL
- MongoDB
- Redis Caching
- Mongoose
- SQL Query Tuning
- ACID Transactions
DevOps & Infrastructure
- AWS (EC2, S3)
- Docker
- Nginx Reverse Proxy
- RabbitMQ Message Broker
- CI/CD Pipelines
Frontend & Mobile
- React.js
- Next.js
- TypeScript
- Tailwind CSS
- React Native
- Expo Ecosystem
System Architecture Visualizer
A simplified version of what a request actually goes through on a typical API of mine — proxy, auth, cache, then the database.
SSL Termination, CORS headers, reverse proxy routing.
IP rate limiting & sanitization checks.
Token validation & role-based validation.
In-memory fast lookup to bypass DB load.
Business logic execution & data transformations.
Asynchronous event worker message queueing.
Write operation with ACID transaction guarantees.
Production Showcases
Pick a project below for the problem it solved, how it's built, and the tech behind it.
ROI Spectrum
Challenge / Context
SEO agencies and website owners lacked an integrated, multi-tenant solution to track ROI, audit logs, service tracking, and automated subscription billing transparently.
System Architecture
Multi-tenant database schema architecture using Node.js/Express backend, React.js frontend, and hybrid storage using PostgreSQL for relational billing data and MongoDB for audit logs.
Results & Accomplishments
Launched at roispectrum.com and running in production since, with query response times cut by 30% through composite indexing and subscription billing fully automated end to end.
Technologies Used
Professional Timeline
Just the one role so far — but the scope grew a lot over it.
Full Stack Developer
Full Stack Developer, working across backend and frontend.
Full Stack Developer
- Took end-to-end ownership of application development across backend systems and frontend interfaces, ensuring scalable architecture and timely delivery.
- Architected and developed ROI Spectrum, a multi-tenant SaaS platform with subscription workflows, service tracking, audit logs, and user-facing dashboards.
- Implemented payment gateway integrations with subscription lifecycle handling, webhook automation, and billing workflows.
- Designed and delivered 200+ RESTful APIs with validation, versioning, and error handling across production systems.
- Optimized APIs and database queries using indexing and aggregation strategies, reducing response time by 30%.
- Implemented role-based access control (RBAC) systems with hierarchical permissions across multiple user roles.
Academic Foundation
A.N. College, Patna
Rank #1 • 8.3 CGPA
Algorithms, databases, compiler design, network security — the database coursework is the part that shows up most in actual work now.
S.G.D.M. College, Patna
Mathematics Honours
The math degree before the MCA — mostly discrete math and statistics, which turned out to be decent prep for reasoning about algorithms later.
Frequently Asked Questions
The questions that come up most often, answered directly.
Want to see the code behind any of this?
Open to full-time backend/full-stack roles and contract work — or just reach out if you have questions about a project above.