I build full-stack applications with a focus on backend engineering, security, and systems that work beyond the happy path.

MCA Scholar · C-DAC Noida (GGSIPU) · Class of 2027

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Arjun Gupta — Software Engineer in progress

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Full-stack engineering · Backend systems · DSA · DevOps

I care about the parts of software engineering that are easy to overlook: authorization boundaries, data consistency, validation, failure handling, and deployment. My projects are where I work through those problems, from designing REST APIs to connecting authentication, databases, and third-party services.

A collaborative coding workspace designed to bring code editing and developer communication together. The project explores the engineering behind a shared development environment, including authentication, database-backed application state, and real-time collaboration.

The engineering focus: managing shared state, designing the data model, organizing application features, and understanding how real-time communication fits into a full-stack system.

Stack: Next.js · TypeScript · Tailwind CSS · PostgreSQL · Prisma · Clerk

flowchart LR
    U["Developers"] --> UI["Next.js Application"]
    UI --> AUTH["Clerk Authentication"]
    UI --> API["Application Logic"]
    API --> DB[("PostgreSQL")]
    API --> RT["Real-time Collaboration"]
    RT <--> U

A food ordering application built as a college team project. It supports customer ordering workflows, restaurant management, menu browsing, and administrative functionality.

The project brings together several backend concerns that are useful beyond a basic CRUD application:

• Authentication and role-based access: Clerk-powered authentication and role-specific customer, restaurant, and admin experiences.
• Order and payment workflows: Razorpay integration, with webhook handling designed around order references and duplicate-event protection.
• Cart management: Redux-based state management with local storage persistence.
• Menu discovery: Filtering by cuisine and vegetarian/non-vegetarian options, alongside pagination.
• Media and notifications: Cloudinary image handling and email notifications through Nodemailer.
• Conversational interface: Gemini-powered food-ordering chatbot.

Stack: React · Node.js · Express.js · MongoDB · PostgreSQL · Clerk · Razorpay · Redux · Cloudinary · Nodemailer · Gemini

flowchart LR
    %% Frontend
    FE["React 18 + Tailwind CSS<br/>Customer UI • Restaurant UI • Admin UI"]

    %% CI/CD
    CI["GitHub Actions<br/>Docker build / deploy"]

    %% Backend API
    subgraph API["Express REST API"]
        direction LR
        SEC["CORS +<br/>Security Headers"]
        AUTH["Clerk Auth<br/>Middleware"]
        ROUTES["Cart / Restaurant /<br/>Menu / User Routes"]
        CTRL["Controllers +<br/>Validation"]
        ORDER["Order &<br/>Payment Logic"]

        SEC --> AUTH --> ROUTES --> CTRL --> ORDER
    end

    %% Database
    DB[("MongoDB<br/>Cart • Restaurant •<br/>Menu • Users • Orders")]

    %% External services
    CLERK["Clerk<br/>Authentication"]
    RAZOR["Razorpay<br/>Payments"]
    CLOUD["Cloudinary<br/>Image Uploads"]
    EMAIL["Gmail<br/>Email"]
    GEMINI["Gemini<br/>Food Chatbot"]

    %% Main request flow
    FE -->|"HTTPS / REST JSON"| SEC
    ORDER <-->|"CRUD"| DB

    %% External service interactions
    CLERK <-->|"Identity / Auth"| AUTH
    ORDER <-->|"Create & verify payments"| RAZOR
    CTRL <-->|"Upload / retrieve images"| CLOUD
    CTRL -->|"Send email"| EMAIL
    ROUTES <-->|"Chatbot requests / responses"| GEMINI

    %% Deployment flow
    CI -.->|"CI/CD • Build & deploy"| API
    CI -.->|"Frontend deployment"| FE

    %% Chatbot UI interaction
    FE -.->|"Chat messages"| GEMINI

    %% Styling
    classDef frontend fill:#17212d,stroke:#aab8c8,color:#f1f5f9,stroke-width:1.5px
    classDef backend fill:#17212d,stroke:#aab8c8,color:#f1f5f9,stroke-width:1.5px
    classDef database fill:#17212d,stroke:#aab8c8,color:#f1f5f9,stroke-width:1.5px
    classDef external fill:#17212d,stroke:#aab8c8,color:#f1f5f9,stroke-width:1.5px
    classDef deployment fill:#17212d,stroke:#aab8c8,color:#f1f5f9,stroke-width:1.5px

    class FE frontend
    class SEC,AUTH,ROUTES,CTRL,ORDER backend
    class DB database
    class CLERK,RAZOR,CLOUD,EMAIL,GEMINI external
    class CI deployment

    style API fill:#202832,stroke:#aab8c8,color:#f1f5f9,stroke-width:2px

A REST API focused on financial records, access control, and predictable request handling. This project is where I work on backend fundamentals that matter when different users need different levels of access to sensitive application data.

What it covers:

• JWT authentication: token-based authentication with password hashing using bcrypt.
• Role-based access control: separate VIEWER, ANALYST, and ADMIN permissions.
• Input validation: Zod schemas for validating incoming data.
• Rate limiting: fixed-window request limiting to reduce excessive traffic.
• Database access: Prisma ORM with PostgreSQL.
• API documentation: Swagger UI through /api-docs.
• Deployment: Docker-based containerization and deployment troubleshooting.

I chose PostgreSQL for its relational data model and transaction guarantees, which suit financial records and structured relationships.

Stack: Node.js · Express.js · PostgreSQL · Prisma · JWT · bcrypt · Zod · Docker · Swagger · Postman

flowchart LR
    Client[Client / Frontend / Postman] -->|HTTP Request| API[Express REST API]
    API --> Middleware[Global Middleware\nCORS + JSON Parsing + Rate Limiter]
    Middleware --> Routes[Route Modules\nAuth / Records / Users / Dashboard]
    Routes --> Controllers[Controllers\nBusiness Logic]
    Controllers --> Auth[JWT Authentication + Role Authorization]
    Controllers --> Prisma[Prisma Client]
    Prisma --> DB[(Supabase PostgreSQL)]

    Auth -->|Validate token| Controllers
    Controllers -->|JSON Response| Client

A technology list tells you what someone has used. The more useful question is how they apply it.

These are the implementation decisions I focus on across my projects:

These are engineering principles reflected in my project work, not a claim that every project implements every item identically.

• Security belongs on the backend. Hiding a button is not authorization. Protected operations need server-side checks.
• Validate at the boundary. Invalid requests should be rejected before they cause inconsistent state.
• Think about retries. Payment callbacks and other external events can be delivered more than once.
• Choose the right data model. Relational integrity and flexible document structures solve different problems.
• Make APIs understandable. Clear resource boundaries, consistent responses, and API documentation improve maintainability.
• Test failure cases. Negative values, missing fields, unauthorized requests, duplicate events, and invalid state transitions deserve attention.
• Learn by shipping. Building, deploying, debugging, and revisiting implementation decisions is part of becoming a better engineer.

I practise DSA consistently to improve problem-solving, algorithmic thinking, and implementation skills.

• LeetCode
• HackerRank

My focus is on understanding the reasoning behind a solution, including time complexity, space complexity, edge cases, and alternative approaches.

• DevOps: Linux fundamentals, Docker, CI/CD, and deployment workflows.
• DSA: Problem-solving patterns, data structures, and algorithm analysis.
• Backend engineering: API design, authentication, authorization, data modeling, and reliability.

Explore more projects, experiments, and development work through my portfolio and GitHub profile.

I also publish articles on DotBlog.