SSL Passthrough

SSL Passthrough is a networking and load balancing technique where encrypted SSL/TLS traffic is forwarded directly to backend servers without decryption at an intermediate proxy or load balancer. This allows the backend servers to handle SSL termination, maintaining end-to-end encryption and offloading SSL processing from the load balancer. It is commonly used in scenarios where backend servers require the original client certificates or need to manage encryption independently.

Also known as: SSL Passthru, TLS Passthrough, SSL Termination Passthrough, SSL Bypass, Encrypted Traffic Passthrough

Why learn SSL Passthrough?

Developers should use SSL Passthrough when backend applications need to process SSL/TLS encryption directly, such as in environments requiring client certificate authentication or when using specific SSL configurations not supported by the load balancer. It is ideal for high-security applications where end-to-end encryption must be preserved, like financial services or healthcare systems, but it increases backend server load as they handle SSL processing.

Learning Resources

• docs: NGINX SSL Passthrough Documentation
• tutorial: HAProxy SSL Passthrough Guide
• tutorial: SSL Passthrough vs Termination Explained
• docs: Kubernetes Ingress SSL Passthrough