LendLite

Role

Full-stack developer

Year

2026

Category

Enterprise

Lending software fails in the details: floating-point money that drifts by a cent, two reviewers approving the same loan, a mobile retry that submits an application twice, or identity documents left on a public URL. A demo-grade CRUD app ignores all of these.

A layered Express API (routes, thin controllers, services, Prisma) with Zod on every input. Money is integer cents, the loan lifecycle is a status machine with an audit trail, approvals and their repayment schedules commit in one transaction, submits are idempotent, and documents are stored privately and streamed through the API after an ownership check. A Next.js front end adds a live repayment calculator, a four-step application wizard, CSV schedule export and an admin dashboard. 89 tests run against a real Postgres, and CI gates every Railway deploy.

Architecture

Highlights

• Money stored as integer cents and rates as basis points (12.50% is 1250), so no amount is ever off by a floating-point fraction.
• Loan status machine (draft, submitted, under review, approved or rejected) enforced in the service layer; invalid moves return 409 and every transition writes an audit row.
• Approval is one database transaction: status, every repayment row and the audit entry commit together, and a conditional update means two admins deciding at once cannot both win.
• Idempotent submit with an Idempotency-Key header: a retried request returns the original result, and reusing a key on another application is rejected.
• Pure amortization engine where the last instalment absorbs rounding, so the final balance is exactly $0.00.
• Private documents on Cloudinary behind the API: ownership checked, 60-second signed links, and uploads verified by MIME type, extension and magic bytes.
• 404 instead of 403 for other users' applications, so IDs cannot be probed; admin stats use a parameterized raw-SQL GROUP BY.
• 89 Jest + Supertest tests against a real Postgres; CI runs typecheck, tests, build, npm audit and a fresh-clone Docker Compose smoke test, and Railway deploys only after CI passes.

Backend tests on a real database

8989

Final balance after rounding

$0.00$0.00

CI jobs gating each deploy

33

Loan statuses, all audited

55

• Next.js 16
• React 19
• TypeScript
• Tailwind CSS 4
• Node.js
• Express
• PostgreSQL
• Prisma
• Zod
• JWT
• bcrypt
• Multer
• Cloudinary
• pino
• Jest
• Supertest
• Docker
• GitHub Actions
• Railway

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