An API gateway proxy sits between your business systems and the Claude API. Every request passes through the gateway before reaching the LLM. The gateway inspects the content, identifies sensitive data patterns — credit card numbers, social security numbers, API keys, internal identifiers — and either redacts, masks, or blocks the data before it reaches Claude. This is a hard guardrail: if the proxy strips a credit card number, Claude physically cannot see it.
Practical implementation
Gateway proxies can range from simple regex-based pattern matching to sophisticated NLP-based entity detection. The right approach depends on the sensitivity of the data and the complexity of the inputs. For most mid-market businesses, a combination of pattern matching for structured data (card numbers, IDs) and entity recognition for unstructured data (names, addresses in free text) provides effective coverage.
The gateway also provides a natural logging point. Every request and its sanitisation actions get recorded, creating an audit trail of what data was intercepted and what reached the LLM. This gives compliance teams visibility into the data protection layer and evidence that sensitive information is being handled correctly.