MongoDB Library Management System

Live demo: https://mongodb-library-management-system.vercel.app

A library management web app built with MongoDB, Node.js/Express and a plain HTML/CSS/JavaScript frontend. It has a dashboard, dark/light themes, and an "Index lab" that shows MongoDB's query plans live.

Requirements covered

5 user-defined functionalities

1. Add Book: the author is found or created in the same transaction; supports multiple copies
2. Register Borrower: email is validated, lower-cased and unique
3. Issue Book: atomic copy reservation, 3-book borrowing limit, custom loan period
4. Return Book: the overdue fine is calculated by MongoDB itself ($$NOW in a pipeline update)
5. View/Search Books: filter, sort and paginate, plus weighted full-text search

5 NoSQL/MongoDB functionalities

Feature	Where to see it
CRUD	Books, borrowers and authors can all be created, read, updated and deleted
Indexing	Unique, compound, case-insensitive (collation), weighted text and partial unique indexes; the Books page shows explain() output comparing the text index with a full collection scan
Aggregation	Dashboard: $facet, $group, $bucket, $dateToString, $lookup, $sort/$limit; pagination uses $facet
Text Search	$text over title (weight 10), author (5) and description (1), ranked by textScore
Data Validation	$jsonSchema with types, ranges, pattern for ISBN/email, plus $expr rules (availableCopies ≤ totalCopies, dueDate > issuedAt)

Extra database features

• Multi-document ACID transactions for issue, return and add-book (falls back to manual rollback on a standalone server)
• Atomic conditional updates (findOneAndUpdate with a filter): two people can't grab the last copy at the same time
• Optimistic locking when editing a book's copy count
• Referencing + denormalisation: books store authorId (joined with $lookup) and a copy of the author's name (for text search)
• Schema migration on startup for data created by older versions of the app
• Window functions: reservation queue positions with $setWindowFields + $documentNumber

Library features

Feature	How it works
Reservations	When every copy is out, borrowers join a queue. A returned copy is held for the first person (heldCopies) for 3 days and they're notified; uncollected holds pass to the next person automatically
Fine payment tracking	Fines are fixed on return; paying records a payments document and marks the loan paid in one transaction. Borrowers owing more than ₹100 can't borrow
Email / SMS reminders	A reminder 2 days before the due date, an overdue notice, and "your reservation is ready". Sent by SMTP / Twilio when configured; always recorded in the notifications outbox
Barcode / QR scanning	Scan desk on Circulation: scan a library card, then a book's ISBN barcode or QR label. It issues or returns automatically. Works with USB scanners, the camera (Chrome/Edge) or typing
Backups	Automatic backup every 24 h (newest 7 kept), "Back up now" and download on the System page, npm run backup / npm run restore
Audit log	Every change is logged with who did it, in the same transaction as the change (Activity page)
Automated tests	npm test: 15 end-to-end tests against a throwaway database, including a 6-way race for the last copy

Collections

Collection	Purpose
books	title, author, authorId, isbn, description, totalCopies, availableCopies, heldCopies, borrowCount
authors	name (unique, case-insensitive)
borrowers	name, email (unique), phone, activeLoans
loans	bookId, borrowerId, issuedAt, dueDate, returned, returnedAt, fine, finePaid, reminder timestamps
reservations	bookId, borrowerId, status (waiting / ready / fulfilled / cancelled / expired), holdUntil
payments	loanId (unique), borrowerId, amount, method, paidAt, receivedBy
notifications	type, channel (email / sms), to, subject, body, status (sent / logged / failed)
auditLogs	at, action, entity, entityId, summary, actor

Database name: library_management

Run

Requires Node.js 20.12+ and MongoDB 6+.

npm install
npm run seed      # optional sample data (refuses to wipe existing data without --force)
npm start

Open http://localhost:3000

npm run dev restarts the server automatically when you edit a file.

Command	What it does
npm test	Runs the automated tests (needs a local MongoDB; uses its own temporary database)
npm run backup	Saves every collection to backups/backup-<time>.json
npm run restore -- backups/<file> --force	Replaces all data with a backup

Configuration

Copy .env.example to .env to change the MongoDB URL, database name, port and library rules. It also explains how to turn on real email (any SMTP server, e.g. Gmail with an app password) and SMS (Twilio). Without them, reminders are still recorded in the outbox on the System page.

Deploying to Vercel

The app runs on Vercel as a serverless function (server.js exports the Express app; vercel.json sets the Mumbai region and a daily cron).

1. Allow access from anywhere (0.0.0.0/0) in MongoDB Atlas → Network Access, because Vercel's IP addresses change.
2. In the Vercel project, add the environment variables MONGO_URI (your Atlas connection string) and CRON_SECRET (any random string).
3. Deploy with vercel deploy --prod, or push to GitHub if the repository is connected.

On Vercel, reminders and reservation-hold expiry run once a day through Vercel Cron (/api/cron), and backups are written to temporary storage, so download them straight away from the System page.

Enabling transactions

Transactions need MongoDB to run as a replica set. A single-node replica set is enough:

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