APIs move everything today: reservations, online orders, card‑issuing requests, payment authorizations, and more. But the moment raw cardholder data appears in any of those API payloads, your entire infrastructure falls into PCI DSS scope — even if you never store the data.

That's exactly the problem PCI Proxy's Filter Proxy solves.

What Is PCI Proxy's Filter Proxy?

By definition, a proxy is an intermediary that sits between two servers. When Server A wants to talk to Server B, it sends its request through the proxy. The proxy forwards the request to Server B, receives the response, and passes it back to Server A. To both servers, it's nearly invisible — they communicate as they always have.

PCI Proxy's Filter Proxy works on this same principle. It's a reverse proxy that sits between you and your partner, intercepting requests and responses in real time, identifying sensitive cardholder data, and tokenizing it before your servers ever see it. Think of it as an intelligent PCI compliance layer that removes cardholder data from your API traffic automatically.

Your integrations work exactly as they do today — no breaking changes, no API rewrites, no modifications. Simply point your traffic to our proxy endpoint, and sensitive cardholder data gets tokenized on the fly, regardless of the API format both servers use. Raw card numbers are replaced with secure, non-sensitive tokens in the background.

How API Tokenization Works: Two Patterns

When servers exchange data, there are two ways a conversation can start: either you fetch data from a partner (pull), or your partner sends data to you (push). The Filter Proxy handles both seamlessly.

Pull: Tokenizing Cardholder Data You Fetch from Partners

Picture this: you're receiving thousands of reservations daily from online travel agencies (OTAs) like Booking.com. Each reservation can include guest names, room preferences, and — in many cases — raw credit card numbers and CVV data. The moment that cardholder data touches your servers, even if you never store it, you're in PCI DSS scope.

With the Filter Proxy, you simply change your API endpoint from Booking.com's URL to ours and add three additional request headers — one of which tells us where to forward the request. We call Booking.com on your behalf, intercept the response before it reaches you, tokenize every sensitive cardholder field, and forward the sanitized payload to your server.

The entire process happens in milliseconds. Your application receives the same API response structure it always has — except the card number is now a token like AEcyq81HSCWWGibU instead of 4111 1111 1111 1111. Same for sensitive authentication data.

Push: Tokenizing Cardholder Data Partners Send to You

Now flip the scenario. Expedia is pushing reservation notifications to you whenever a guest books one of your properties. Traditionally, those requests arrive at your API endpoint with the full payload — including raw cardholder data — putting you directly in PCI scope.

With the Filter Proxy, you give Expedia a dedicated push endpoint URL hosted by PCI Proxy. Their reservation requests arrive at our servers first. We parse the payload in real time, tokenize every sensitive cardholder field, and forward the sanitized request to your actual API endpoint.

From your server's perspective, it looks like a normal request from Expedia — same structure, same data — except the card number is now a secure token. No raw cardholder data ever reaches your infrastructure.

Why Companies Use PCI Proxy to Reduce PCI DSS Scope

The same approach applies across industries: e-commerce platforms managing payment flows, fintechs building card programs, fraud providers analyzing transaction patterns, airlines managing bookings via GDS or NDC, and more. Any time your system receives raw cardholder data via API — regardless of whether you store it — you're in PCI DSS scope.

With PCI DSS v4.0.1 introducing stricter API security requirements and data breaches at an all-time high, reducing your cardholder data environment (CDE) isn't just smart — it's essential.

Key benefits of PCI Proxy's Filter Proxy:

• Simplified PCI DSS Compliance — Sensitive cardholder data never touches your servers, dramatically shrinking your compliance scope.
• Zero Integration Overhead — No code changes required. Route traffic through our proxy and configure which fields to tokenize.
• Works With Any Partner — Booking.com, Expedia, Amadeus, Sabre, Marqeta, or any custom integration.
• Universal Token Format — One consistent token format that works across your entire payment stack, eliminating the complexity of managing tokens from multiple providers.
• Reduced Breach Risk — Cardholder data that never enters your infrastructure can never be compromised in a breach.

Get Started: Remove Cardholder Data from Your API Traffic

Ready to reduce your PCI DSS scope and eliminate cardholder data from your infrastructure?

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