The 'One Amazon' Fallacy: Engineering Global Affiliate Traffic

I recently spent a week fighting with the Amazon Affiliate program. I thought it would be simple: get a link, paste it, profit.

I was wrong. I fell into the trap of thinking “Amazon is Amazon.”

The “One Amazon” Fallacy

Here is the reality: To a user in London, amazon.com is a foreign website. To a user in Berlin, it’s virtually useless.

If I send a German user to the US store, three things happen, and they are all bad:

1. Shipping Shock: They see “Does not ship to Germany” or massive international shipping fees. They leave.
2. Commission Leak: They manually switch to amazon.de to buy the item. Because the session didn’t carry over, I get $0.
3. Trust Damage: Showing prices in USD ($) to a European user looks unprofessional.

To make this work, I needed to treat the US, UK, and Germany as three separate universes.

The Engineering Solution

I decided to support the “Big Three” initially: US (United States), GB (United Kingdom), and DE (Germany).

Step 1: The Paperwork (Again)

There is no “Global Account.” I had to register for Amazon Associates separately in the US, UK, and Germany.

• Three sign-ups.
• Three tax interviews (W-8BEN).
• Three bank account configurations.

It’s tedious, but necessary to get the unique Affiliate Tags for each region.

Step 2: Smart Routing with Vercel

Since my site is hosted on Vercel, I can use their edge network to detect where a user is coming from without slowing down the page.

Vercel provides a request header called x-vercel-ip-country. I use this to dynamically swap the Amazon domain and my affiliate tag.

Here is the logic I implemented:

const REGION_CONFIG = {
  US: {
    domain: "amazon.com",
    currency: "$",
    tagEnv: "AMAZON_TAG_US", // My US Store ID
  },
  GB: {
    domain: "amazon.co.uk",
    currency: "£",
    tagEnv: "AMAZON_TAG_GB", // My UK Store ID
  },
  DE: {
    domain: "amazon.de",
    currency: "€",
    tagEnv: "AMAZON_TAG_DE", // My German Store ID
  },
};

// Default to US if country is unknown
const region = REGION_CONFIG[userCountryCode] || REGION_CONFIG.US;

Now, when a user from London visits, the site automatically renders amazon.co.uk links with my UK tag.

Step 3: The Safety Net (OneLink)

Even with code handling the routing, I set up Amazon OneLink. This is Amazon’s internal tool that links your international accounts. It acts as a fallback. If my code fails to detect the IP, or if a user shares a link with a friend overseas, OneLink attempts to redirect them to their local store.

Conclusion

Building a global product (even a tiny one) means respecting the user’s physical reality. You can’t just ship US-centric code and expect the world to adapt.

It was a headache to set up, but now the plumbing is truly global. A click in Berlin stays in Berlin. A click in New York stays in New York.

And hopefully, the coins drop into the right buckets.