Understanding AWS Pricing

AWS charges for what you use. For Lambda + API Gateway, here’s what costs money.

Lambda Pricing

Free tier (always free):

• 1 million requests per month
• 400,000 GB-seconds of compute time per month

After free tier:

• $0.20 per 1 million requests
• $0.0000166667 per GB-second

What is a GB-second? Memory (GB) × execution time (seconds).

Example:

• Function uses 512 MB (0.5 GB)
• Runs for 200ms (0.2 seconds)
• Cost: 0.5 GB × 0.2 seconds = 0.1 GB-second

For 1 million requests:

• 0.1 GB-second × 1,000,000 = 100,000 GB-seconds
• Within free tier (400,000 GB-seconds limit)

For small projects: You’ll likely stay in the free tier.

API Gateway Pricing

HTTP API (what we used):

• Free tier: First 1 million requests per month
• After: $1.00 per 1 million requests

REST API (older, more features):

• Free tier: First 1 million requests per month
• After: $3.50 per 1 million requests

Data transfer:

• First 1 GB per month free
• After: $0.09 per GB

For small projects: You’ll likely stay in the free tier.

Real-World Cost Example

Scenario: Your API gets 10,000 requests per month.

Lambda:

• Requests: 10,000 (free)
• Compute: ~5,000 GB-seconds (free)
• Cost: $0

API Gateway:

• Requests: 10,000 (free)
• Data transfer: ~100 MB (free)
• Cost: $0

Total: $0 (within free tier)

If you get 2 million requests:

• Lambda: 1M free + 1M × $0.20 = $0.20
• API Gateway: 1M free + 1M × $1.00 = $1.00
• Total: $1.20

Still very cheap.

Why Serverless is Cheap for Small Projects

Traditional server (EC2):

• $7.20/month minimum (even with 0 requests)
• You pay for 24/7 uptime

Serverless (Lambda + API Gateway):

• $0 for low traffic (free tier)
• Pay only when used

Break-even point: Around 1-2 million requests per month. Below that, serverless is cheaper.

Understanding What You Might Be Billed For

Lambda:

• Requests (after free tier)
• Compute time (after free tier)
• Data transfer out (usually free for small amounts)

API Gateway:

• Requests (after free tier)
• Data transfer (after free tier)

Other services (if you add them):

• CloudWatch Logs: First 5 GB free, then $0.50/GB
• DynamoDB: Free tier available
• S3: Free tier available

For this tutorial: Everything should be free (within free tier).

Cleanup Checklist

When you’re done experimenting, clean up to avoid unexpected charges.

Step 1: Delete API Gateway

1. Go to API Gateway
2. Select your API
3. Click “Actions” → “Delete”
4. Confirm deletion

Why: API Gateway itself doesn’t cost much, but it’s good practice to clean up.

Step 2: Delete Lambda Function

1. Go to Lambda
2. Select your function
3. Click “Actions” → “Delete”
4. Confirm deletion

Why: Lambda is free for low usage, but delete if you’re not using it.

Step 3: Delete CloudWatch Log Groups

1. Go to CloudWatch → Log groups
2. Find /aws/lambda/notes-api (or your function name)
3. Select it
4. Click “Actions” → “Delete log group”
5. Confirm

Why: Logs cost money after the free tier (5 GB). Delete old logs.

Step 4: Verify No Charges

1. Go to AWS Billing Dashboard
2. Check “Current charges”
3. Should be $0 (within free tier)

Note: AWS bills monthly. Check again next month to be sure.

Responsible Cloud Use

Best practices:

• Delete resources when done experimenting
• Set up billing alerts (get notified if charges exceed threshold)
• Use free tier when possible
• Monitor usage in AWS Cost Explorer

Billing alerts:

1. Go to AWS Billing → Preferences
2. Enable “Receive Billing Alerts”
3. Go to CloudWatch → Alarms
4. Create billing alarm (e.g., alert if charges > $5)

What If You Want to Keep It Running?

If you want to keep your API running:

Option 1: Keep it as-is

• Monitor usage
• Stay within free tier
• Delete if you stop using it

Option 2: Add monitoring

• Set up CloudWatch alarms
• Monitor request count
• Get alerts if usage spikes

Option 3: Add a database

• Use DynamoDB (free tier available)
• Store notes persistently
• Still likely free for small projects

Key Takeaways

Before the final summary:

1. Lambda + API Gateway are cheap - Free tier covers most small projects
2. Pay per use - Only pay when code runs
3. Clean up when done - Delete functions, APIs, and logs
4. Monitor usage - Set up billing alerts
5. Free tier is generous - 1M requests/month for Lambda, 1M for API Gateway

What’s Next?

In the final page, we’ll summarize what you learned and suggest next steps for building on this foundation.