How to Make Cursor Follow Serverless Best Practices

1---
2description: AWS Lambda serverless best practices
3globs: "**/handlers/**, **/lambdas/**, **/functions/**"
4alwaysApply: false
5---
6
7- Initialize SDK clients and DB connections OUTSIDE the handler (module scope)
8- Handler function must be stateless — no global mutable state between invocations
9- Use environment variables for all configuration (process.env)
10- Keep handler functions under 50 lines — extract logic to separate modules
11- Return proper API Gateway response format: { statusCode, headers, body }
12- Always include CORS headers in responses
13- Use structured JSON logging (not console.log with strings)
14- Import only what you need: import { S3Client } from '@aws-sdk/client-s3'
15- Never import entire AWS SDK v2: import AWS from 'aws-sdk' is FORBIDDEN
16- Set timeout handling: check context.getRemainingTimeInMillis()
17- Wrap handler in try/catch with proper error response formatting

1// Prompt to type in Cursor Composer (Cmd+I):
2// @serverless.yml @src/types/order.ts
3// Generate an API Gateway Lambda handler at src/handlers/createOrder.ts
4// Requirements:
5// - POST /orders endpoint
6// - Parse and validate request body using zod
7// - Insert order into DynamoDB (table from ORDER_TABLE env var)
8// - Return 201 with created order, 400 for validation errors, 500 for server errors
9// - Initialize DynamoDB client at module scope (outside handler)
10// - Include CORS headers
11// - Use structured JSON logging
12// - Add timeout awareness with context.getRemainingTimeInMillis()

1// Prompt to type in Cursor Chat (Cmd+L):
2// @src/handlers/createOrder.ts
3// Review the imports in this Lambda handler for bundle size.
4// Replace any broad imports with targeted imports:
5// - AWS SDK v3: import specific clients, not entire packages
6// - lodash: import individual functions, not the whole library
7// - moment: replace with date-fns or native Date methods
8// List each change and explain the bundle size impact.

1// Prompt to type in Cursor Composer (Cmd+I):
2// @src/handlers/createOrder.ts
3// Generate a Lambda middleware module at src/middleware/index.ts
4// Include middleware for:
5// 1. JSON body parsing with error handling
6// 2. CORS headers (configurable origins)
7// 3. Request validation using zod schemas
8// 4. Structured error response formatting
9// 5. Request ID logging from API Gateway context
10// Use the middy pattern or a simple wrapper function.
11// Show how to apply middleware to the createOrder handler.

1// Select a handler file, press Cmd+K:
2// Replace all console.log calls with structured JSON logging.
3// Each log entry must include:
4// - timestamp, level (INFO/WARN/ERROR), message
5// - requestId from the Lambda context
6// - Additional context as structured fields (not string concatenation)
7// - Error logs must include stack trace as a separate field
8// Format: JSON.stringify({ timestamp, level, message, requestId, ...data })