Boosting API Performance with CloudFront Caching: A Practical Guide

Modern cloud applications rely heavily on API performance. Whether you’re running serverless APIs through API Gateway or containerized services behind a Load Balancer, every request that hits your backend consumes compute, increases latency, and adds cost.

If your users are spread across multiple regions, that latency becomes even more noticeable. Requests travel all the way to your origin just to return data that often hasn’t changed.

This is exactly why placing CloudFront in front of your API Gateway or Load Balancer is one of the smartest optimizations you can make.

Why CloudFront Makes Your API Faster and Cheaper

1. Lower Latency

CloudFront serves responses from edge locations closest to your users.
No cross-region hops. No unnecessary travel. Just instant responses.

2. Reduced Load on Your Backend

Cached responses never hit API Gateway, Lambda, ALB, or EKS.
Your infrastructure only processes fresh or non-cacheable requests.

3. Increased Throughput

With duplicated load removed, your backend has more capacity for real traffic — not repeated calls.

4. Significant Cost Savings

CloudFront is cheaper than API Gateway or Load Balancers on a per-request basis.
The fewer origin requests you serve, the lower your AWS bill.

5. Better Security with AWS WAF

You can attach AWS WAF directly to CloudFront, protecting your API before traffic ever reaches your VPC.

How the Architecture Works

Depending on your application, CloudFront sits in front of:

Serverless

CloudFront → API Gateway → Lambda

Containers / EC2 / Kubernetes

CloudFront → Application Load Balancer → EKS / ECS / EC2

CloudFront handles:

• Caching

• SSL termination

• WAF protection

• Compression

• Regional edge routing

• Path-based cache rules

All while drastically reducing how often your backend gets hit.

Choosing the Right Origin

CloudFront supports several origin types:

• API Gateway (REST or HTTP APIs)

• Application Load Balancer

• S3 Buckets

• Static websites

For API workloads, you’ll typically select either:

API Gateway endpoint URL
or
ALB DNS name

Cache Behavior Configuration

Cache behaviors let you fine-tune how CloudFront handles traffic.

You can set caching rules for:

• Entire API (*)

• Specific endpoints (/products/*, /auth/*, /search/*)

• Static vs dynamic routes

Each behavior can specify:

• Min TTL

• Max TTL

• Default TTL

• Forwarded headers

• Query strings

• Cookies

• Allowed HTTP methods

If your API doesn’t send caching headers, CloudFront uses the TTLs you set here.

Understanding Cache TTL (Time To Live)

You control caching in two places:

1. From Your Backend (Preferred)

Set headers such as:

Cache-Control: public, max-age=3600

2. From CloudFront

Override TTL with:

• Minimum TTL

• Maximum TTL

• Default TTL

CloudFront will use whichever setting is the strictest.

Handling Cached Error Responses

CloudFront caches HTTP errors (4xx/5xx) for 10 seconds by default.
This can be changed using Custom Error Responses if you want shorter or longer caching behavior.

Dealing With Updates & Cache Invalidation

When resources rarely change, you can set large TTLs — even hours or days.

But once something does update, you need a way to clear stale cache.

Here are two best strategies:

1. Programmatic Invalidation

After a successful update, call:

aws cloudfront create-invalidation \
  --distribution-id ABC123 \
  --paths "/resource/*"

This ensures any subsequent requests get fresh data.

2. Versioned URLs

Useful for metadata or static data:

/api/v1/products
/api/v2/products

Old versions stay cached, new versions fetch fresh data without manual invalidation.

Final Thoughts

Adding CloudFront caching in front of your API Gateway or Load Balancer is one of the simplest and most impactful improvements you can make:

• Faster global response times

• Reduced backend load

• Higher throughput

• Lower AWS infrastructure costs

• Optional WAF protection at the edge

If you're running modern, globally accessed APIs — this upgrade should be at the top of your optimization list.