Intercepting and Redacting PII in Postgres with a Binary Protocol Proxy

The queries hit hard and fast, billions in a day, each carrying data you can’t afford to leak. It’s not text over HTTP. It’s raw, binary, high‑performance connections straight into Postgres. Somewhere in that stream is PII data — names, emails, IDs — and every byte is a liability if you can’t control it.

Postgres uses a binary protocol to talk to clients. It’s faster than text, smaller to transmit, and harder for middle layers to parse without specialized tooling. Proxying that protocol means intercepting packets between the client and server, decoding them, applying rules, and optionally rewriting or blocking sensitive fields before they hit storage or leave your network.

When the data in question contains personally identifiable information (PII), proxying isn’t optional. Every SELECT, INSERT, and UPDATE can carry sensitive payloads. That is why a Postgres binary protocol proxy must handle:

• Full protocol parsing — startup, query, and data messages
• Streaming interception — without breaking the client’s connection or transaction integrity
• Transparent modification — redacting or masking PII in flight
• Logging with zero‑knowledge storage — separating metadata from actual PII content

You can’t rely on application‑level filtering alone. Applications change. Teams deploy features fast. The database stays, and it sees everything. A binary protocol proxy is the enforcement point that lives at the edge, not in the app code.

Engineering it requires a deep map of Postgres wire formats. The frontend/backend messages — Query, Parse, Bind, DataRow, RowDescription, ErrorResponse — all carry structured binary data with predictable offsets. PII detection at this level means fast pattern matching, column metadata lookups, and efficient buffer slicing. Masking or blocking needs write‑back logic to replace values without corrupting alignment.

Deploying such a proxy in production means accounting for TLS, authentication forwarding, connection pooling, and replication compatibility. Latency budget is tight; every millisecond counts. Scale testing must push tens of thousands of concurrent connections and multi‑gigabyte result sets.

The payoff: centralized, protocol‑level control over PII in Postgres. No code changes in clients. No trust gap between services. You decide exactly what leaves the database, in real‑time, at packet speed.

See this in action with hoop.dev. Stand up a Postgres binary protocol proxy that can intercept, inspect, and redact PII data in minutes — live.