Careeroza

Data Flow

Reading

Browser ── GET /products/redmi-note-14-42 ──► CDN / Next.js
                                               │ static shell cached? ──yes──► send shell
                                               ▼
                         page.tsx (Server Component)
                               │ getProduct(42)  ── lib/dal/products.ts ('use cache', tag product-42)
                               │                         │
                               │                         ▼
                               │                   Prisma ──► PostgreSQL
                               ▼
                 HTML shell + streamed <DeliveryEstimate/> (cookie: pincode)
                               ▼
               Browser hydrates AddToCartButton, Gallery (client)

Writing

AddToCartButton (client) ── addToCart(42, 1) [Server Action, POST] ──► server
                                                                     │ auth / guest cart cookie
                                                                     │ lib/dal/cart.ts  ──► PostgreSQL
                                                                     │ revalidatePath('/cart')
Navbar badge updates  ◄──── action result + fresh RSC payload ──────┘

Razorpay ── POST /api/webhooks/razorpay (HMAC verified) ──► markOrderPaid ──► revalidateTag('orders-u1')

Order Total, End to End

Example

The checkout summary combines several rules from this material (paise to avoid float errors, coupon, delivery fee, GST shown inclusive):

type CartLine = { name: string; pricePaise: number; qty: number };

const rupees = (p: number) => '₹' + (p / 100).toLocaleString('en-IN', { minimumFractionDigits: 2 });

function summary(lines: CartLine[], coupon: { code: string; percent: number; maxPaise: number } | null) {
  const subtotal = lines.reduce((s, l) => s + l.pricePaise * l.qty, 0);
  const discount = coupon ? Math.min(Math.round((subtotal * coupon.percent) / 100), coupon.maxPaise) : 0;
  const delivery = subtotal - discount >= 49900 ? 0 : 4000;
  const total = subtotal - discount + delivery;
  const gstIncluded = Math.round(total - total / 1.18); // 18% GST already inside the price
  return { subtotal, discount, delivery, total, gstIncluded };
}

const s = summary(
  [{ name: 'Clean Code', pricePaise: 45000, qty: 1 }, { name: 'USB-C Cable', pricePaise: 29900, qty: 2 }],
  { code: 'BOOKS10', percent: 10, maxPaise: 10000 },
);
for (const [k, v] of Object.entries(s)) console.log(k.padEnd(12), rupees(v));

Output

subtotal     ₹1,048.00
discount     ₹100.00
delivery     ₹0.00
total        ₹948.00
gstIncluded  ₹144.61