Shipping rate calculator

Architecture

[Seller UI] → [API Gateway] → [AWS Lambda] → [Courier APIs] ↓ [RDS / DynamoDB / S3]

Frontend: Nextjs form

Working

Sends a POST request to your API Gateway endpoint with:

code colelct form in json
{
  "pickup_pincode": "560001",
  "delivery_pincode": "400001",
  "weight": 2.5,
  "dimensions": {"l": 12, "b": 10, "h": 8},
  "quantity": 1
}

Hosted on cloudflare pages

Backend with Lambda

Working

Your AWS Lambda function will:

1. Receive the payload from API Gateway

2. Call 4–5 courier partner APIs concurrently (using asyncio or ThreadPoolExecutor)

3. Return a unified JSON response with rates and delivery times

Example (Python/FastAPI-like Lambda handler):

import json, asyncio, httpx

async def call_delhivery(data):
    async with httpx.AsyncClient() as client:
        resp = await client.post("https://api.delhivery.com/rate", json=data)
        return {"partner": "Delhivery", "rate": resp.json().get("rate")}

async def call_bluedart(data):
    async with httpx.AsyncClient() as client:
        resp = await client.post("https://api.bluedart.com/rate", json=data)
        return {"partner": "Bluedart", "rate": resp.json().get("rate")}

def lambda_handler(event, context):
    data = json.loads(event["body"])
    results = asyncio.run(asyncio.gather(
        call_delhivery(data),
        call_bluedart(data)
    ))
    return {
        "statusCode": 200,
        "headers": {"Content-Type": "application/json"},
        "body": json.dumps({"rates": results})
    }

✅ Fast cold start (Python 3.10/3.11 runtime) ✅ Concurrent API calls → low latency ✅ Serverless → no infra management

API Gateway

API Gateway

• Create a REST API in AWS API Gateway.

• Connect /rates endpoint to the Lambda.

• Enable CORS so your frontend can call it directly.

• Add rate limiting or usage plans (100/day is trivial).

---

Step 2: Create API Gateway

1. Go to API Gateway → Create API

   • Choose “REST API”

   • Select “Build”

   • Name: shipping-rate-api

   • Endpoint Type: Regional

2. Create a Resource

   • Click Actions → Create Resource

   • Name: rates

   • Resource Path: /rates

3. Create a Method

   • Under /rates, click Create Method → POST

   • Integration type: Lambda Function

   • Choose your Lambda: shipping-rate-calc

   • Save → Allow permission

4. Enable CORS

   • Select /rates → Actions → Enable CORS

   • Set:

     • Allowed Origins: * (or restrict to your frontend domain)

     • Allowed Methods: POST

     • Allowed Headers: Content-Type, Authorization

5. Deploy the API

   • Actions → Deploy API

   • Create a new Stage: prod

You’ll get an endpoint like:

Collect logs/data

import boto3, time

dynamodb = boto3.resource("dynamodb")
table = dynamodb.Table("rate_logs")

table.put_item(Item={
    "id": str(time.time()),
    "pickup": data["pickup_pincode"],
    "delivery": data["delivery_pincode"],
    "rates": results
})

Security

• Store courier API keys in AWS Systems Manager Parameter Store or Secrets Manager

• Lambda retrieves them securely at runtime:

Testing

test with FASTAPI Swagger UI