Bablu Kumar Singh
Backend-Focused Full Stack Developer
Writing about backend engineering — Node.js, Express, PostgreSQL/MongoDB, and whatever comes up building SaaS systems and, more recently, React Native apps.
Bablu Kumar Singh
Backend & Full Stack Engineer
Noida, UP, India
Professional Summary
2 years in now, most of it spent building and maintaining backend systems for production SaaS products — API design, payment gateway integrations, and keeping data consistent across PostgreSQL and MongoDB. A good chunk of that time, at X-Strategy Services LLP, went into ROI Spectrum: a multi-tenant dashboard where getting the permissions model right (who can see what, across which tenant) mattered as much as the APIs themselves.
Now at Dextrous Infosolution in Noida Sector 62, and applying some of that same backend discipline — offline-first data, sync conflicts, local storage — to mobile work with React Native and Expo.
Technical Skills
The stack in day-to-day use, split roughly by where it sits — frontend, backend, data, infra, and mobile.
Frontend
Backend
Databases
Messaging
Cloud & DevOps
Mobile
Professional Experience
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.
Specialized Domains
Three areas that overlap more than they used to: backend systems, the full-stack SaaS work built on top of them, and the mobile side that's newer.
Backend Expertise
Most of the day-to-day: API design, input validation, and keeping response times reasonable as data grows.
- •Database indexing & optimization for 30% reduction in query latencies.
- •Lightweight Redis caching & rate limiting policies protecting server threads.
- •Asynchronous broker routing with RabbitMQ pipelines handling background processing.
Full Stack Expertise
Wiring the backend up to a React/Next.js frontend and making sure the parts that touch money — billing, subscriptions — don't break quietly.
- •Multi-tenant SaaS dashboard (ROI Spectrum) separating database tenants cleanly.
- •Stripe integration with automated subscription billing and secure webhooks.
- •Zod schemas validating form payloads on client-side and endpoint interfaces.
Mobile Journey
The newest area — React Native and Expo, mostly figuring out what "offline-first" actually requires once real sync conflicts show up.
- •Local database caching using SQLite inside React Native apps.
- •Offline-first replication patterns queueing server requests.
- •Push notification triggers utilizing Expo Client SDK.
Featured Projects
A few things worth pointing to directly, permissions and billing included.
ROI Spectrum
SEO agencies and website owners lacked an integrated, multi-tenant solution to track ROI, audit logs, service tracking, and automated subscription billing transparently.
Forklift CRM
Operations managers struggled to handle lead assignments, track workflow automations, and manage sales representatives with clean role-based permissions.
AgentCore
Every LLM provider ships its own SDK, message format, and streaming API, so switching models, or falling back to a second provider when one is rate-limited, usually means rewriting the integration layer.
Latest Articles
Recent write-ups — query tuning, permissions, and API design mostly.
How AI Actually Works (A Beginner's Guide)
When I first heard terms like tokens, embeddings, self-attention, and transformers, they sounded complicated. After my first class on Generative AI and Agentic AI, I realized these concepts aren't as difficult as they seem. Here's how modern AI models like ChatGPT actually work, explained as simply as I can manage.
React Native Learning Journey: A Backend Developer's Perspective
A backend developer's honest journey into React Native with Expo — covering the mental model shift, navigation, state management, API integration, and how backend skills transfer to mobile development.
AWS for Backend Developers: Essential Services and Architecture Patterns
A backend developer's guide to essential AWS services — covering EC2, RDS, S3, SQS, CloudFront, and building a production-ready deployment architecture with Auto Scaling and load balancing.
Academic Foundation
A.N. College, Patna
Rank #1 • 8.3 CGPA
Covered algorithms, database systems, compiler design, and network security — the database and algorithms coursework turned out to be the part that stuck.
S.G.D.M. College, Patna
Mathematics Honours
Discrete math and statistics before the MCA — not directly related to backend work day to day, but it's where the comfort with algorithmic thinking started.
Curriculum Vitae
Full work history as a PDF, if the page version isn't enough.
Have something to build?
Open to full-time backend/full-stack roles, contract work, and the occasional "our queries are slow, help" consult.