The Budget-Friendly Monolith: Rails File Uploads with Cloudflare R2

If you have been using AWS S3 for your Rails file uploads, you know the pain of the monthly bill. It’s not just the storage cost; it’s the Egress Fees. Every time a user downloads a file or views an image, AWS charges you for the data leaving their servers.

For a solo developer or a small startup, these "hidden" fees can grow very fast.

In 2026, the best alternative is Cloudflare R2. It is an object storage service that is 100% compatible with the S3 API, but with one massive advantage: Zero Egress Fees. You only pay for the space you use.

Because it uses the S3 API, setting it up with Rails ActiveStorage is incredibly easy. Here is how to do it in 4 steps.

STEP 1: The Credentials

First, log into your Cloudflare dashboard and create a new R2 Bucket.

Once the bucket is created, you need to generate "API Tokens."

1. Go to R2 > Manage R2 API Tokens.
2. Create a new token with Edit permissions.
3. Save your Access Key ID, Secret Access Key, and the Jurisdiction-specific endpoint.

The endpoint will look something like this:
https://<account_id>.r2.cloudflorage.com

STEP 2: The Gems

Even though we are using Cloudflare, we still use the official AWS S3 gem because Cloudflare built R2 to be a "drop-in" replacement.

Add this to your Gemfile:

gem "aws-sdk-s3", require: false

Run bundle install.

STEP 3: Configuration (storage.yml)

Now we need to tell Rails how to talk to the R2 bucket. Open your config/storage.yml and add a new section for Cloudflare.

# config/storage.yml
cloudflare:
  service: S3
  access_key_id: <%= ENV['CLOUDFLARE_R2_ACCESS_KEY_ID'] %>
  secret_access_key: <%= ENV['CLOUDFLARE_R2_SECRET_ACCESS_KEY'] %>
  region: auto # R2 handles regions automatically
  bucket: my-app-uploads
  # This is the endpoint you got from Step 1
  endpoint: https://<account_id>.r2.cloudflarestorage.com
  force_path_style: true

Note: Make sure to add those ENV variables to your .kamal/secrets or your production server!

STEP 4: Tell Rails to use R2

Finally, update your production environment to use the new service.

# config/environments/production.rb
config.active_storage.service = :cloudflare

Bonus: Enabling Direct Uploads (CORS)

In a previous article, I talked about Direct Uploads to save your server from freezing. If you want to use Direct Uploads with R2, you must configure CORS (Cross-Origin Resource Sharing).

Cloudflare makes this easy. Go to your Bucket settings in the dashboard and paste this JSON into the CORS section:

[
  {
    "AllowedOrigins": ["https://yourdomain.com"],
    "AllowedMethods": ["GET", "PUT", "POST"],
    "AllowedHeaders": ["*"],
    "ExposeHeaders": ["Content-Type", "ETag"]
  }
]

This tells Cloudflare: "It is safe to let users from my website upload files directly to this bucket."

Summary

Switching from AWS S3 to Cloudflare R2 is one of the smartest "business" moves a solo developer can make.

1. Compatibility: You don't have to change your Ruby code.
2. Predictability: No more surprise bills because an image went viral.
3. Simplicity: One less AWS console to navigate.

By combining Rails 8, Kamal 2, and Cloudflare R2, you are building a production stack that is fast, secure, and incredibly cheap to run.