Cache invalidation

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Goal

After this page you will know why CloudFront caches the old page and how to flush it with one CLI command after redeploying index.html.

Prerequisites

• Fetch from the page — the updated index.html is uploaded to S3.

Why the old page stays

CloudFront is a CDN — it stores a copy of your files at dozens of edge locations around the world so readers get them from the nearest server rather than reaching all the way to S3 in us-east-1. That copy is called a cache entry.

When you upload a new index.html to S3, the edge caches do not know about it. They keep serving the old copy until one of two things happens:

• The TTL (time-to-live) on the cached object expires and the edge fetches a fresh copy from S3.
• You send an invalidation request that tells CloudFront to discard the cached copy immediately.

The default TTL for an S3-origin distribution can be 24 hours. Waiting that long after every redeploy is impractical. Use an invalidation instead.

Invalidate the cache

# EXAMPLE123DIST is a PLACEHOLDER distribution id — use your own.
aws cloudfront create-invalidation \
  --distribution-id EXAMPLE123DIST \
  --paths "/index.html"

EXAMPLE123DIST is a placeholder. Find your real distribution ID in the CloudFront console (it looks like E1ABCD2EFGHIJK) or by running:

aws cloudfront list-distributions --query 'DistributionList.Items[*].[Id,DomainName]' --output table

After the invalidation completes (usually under 60 seconds), all edge locations will fetch the new index.html from S3 on the next request.

Cost

Each invalidation request is free for the first 1,000 paths per month. One path (/index.html) counts as one. For the low deployment frequency of a learning project this is always free.

Verify

Open your CloudFront URL in a browser (or use curl). You should see the updated page that calls the API and renders the item list. If you see the old static content, wait 30 seconds and try again — the invalidation may still be propagating.

Next → Safety and placeholders