I’m Md. Mehedy Hasan Tanvir, a Senior Full-Stack JavaScript Engineer focused on building and operating reliable, production-grade SaaS systems.
Based in Mymensingh, Bangladesh.
I work on end-to-end web systems with an emphasis on backend architecture, data integrity, and long-term maintainability.
My background includes designing APIs, implementing authentication and payment flows, managing deployments, and supporting live production systems with real users. Earlier MERN-based projects laid the groundwork for my current focus on scalable backend systems and SaaS engineering.
Currently working as a Full-Stack Developer at FlowAppz, with ownership over backend APIs, SaaS features, deployments, and production stability.
Scalable backend system design, strong type modeling, and cross-platform product architecture.
Thoughtful collaboration on product-focused or SaaS-oriented work where engineering quality and ownership matter.
Continuously improving system design decisions, code quality, and operational reliability — while sharing experience and guidance where helpful.
I enjoy mentoring and helping engineers think more clearly about system design.
These projects were built earlier in my career.
I present them here as foundational systems that shaped my current approach to backend engineering, security, and system design.
Context
An early full-stack platform that introduced real-world challenges around role-based access control, payments, and API ownership.
System Scope
- Multi-role architecture (Admin, Tour Guide, Tourist)
- JWT-based authentication and authorization
- Stripe payment processing
- RESTful backend with MongoDB and Mongoose
- Axios interceptors for request and error handling
Key Learnings
- Authorization rules must be enforced centrally
- Payment flows require strict backend validation
- Early schema decisions have long-term impact
🔗 Client: https://github.com/Mehedy-Tanvir/destinize-travel-guide
🔗 Server: https://github.com/Mehedy-Tanvir/destinize-travel-guide-server
🔗 Live: https://destinize-tour-guide.web.app/
Context
A marketplace system that highlighted the importance of defensive backend design and API safety.
System Scope
- JWT-protected APIs and private routes
- Custom middleware for MongoDB ObjectID validation
- Centralized error handling via Axios interceptors
- Provider-side workflow management
Key Learnings
- Input validation is critical to server stability
- Middleware is essential for enforcing invariants
- Backend failures directly affect user trust
🔗 Client: https://github.com/Mehedy-Tanvir/tour-guide-client
🔗 Server: https://github.com/Mehedy-Tanvir/tour-guide-server
🔗 Live: https://travello-local-guide.web.app/
Context
An early commerce-style application focused on authentication boundaries and user-scoped data.
System Scope
- Firebase authentication
- Protected routes and private data access
- CRUD workflows for products and carts
- Persistent UI state management
Key Learnings
- Authentication and authorization solve different problems
- User data must always be scoped server-side
- Clear separation of concerns reduces refactor cost