A common justification for bypassing TLS inspection is performance impact, particularly on latency-sensitive operations like user authentication. I decided to quantify this cost in a controlled FinOps context, measuring the overhead of TLS 1.3 decryption/inspection within a SASE framework on application login latency.
The test environment consisted of a simulated SaaS application. I measured average login transaction times under three conditions:
* Direct connection (no proxy/inspection)
* SASE proxy with TLS 1.3 inspection disabled (passthrough)
* SASE proxy with full TLS 1.3 inspection enabled
The results were revealing. Compared to the direct connection baseline, the inspection-added latency was non-trivial but concentrated:
* **TLS handshake phase:** Added 120-180ms. This is the primary cost of the extra key exchanges and policy checks.
* **Application login payload transfer:** Negligible added latency (<10ms).
* **Overall login transaction increase:** A consistent 22-28% increase in total time from initiation to session establishment.
From a cloud cost perspective, this has two implications. First, the latency overhead could translate to increased compute resource consumption for user-facing services to maintain performance SLAs. Second, and more critically, it forces a clear cost-benefit analysis: is the security value of inspecting this particular encrypted traffic worth a predictable 25% latency penalty for every authenticated transaction? For internal applications with low risk profiles, the cost may outweigh the benefit. For high-risk external-facing apps, it might be justified.
My recommendation is to apply the same principles used for rightsizing instances:
* **Categorize applications by risk and performance sensitivity.**
* **Establish inspection policies accordingly, bypassing low-risk, high-performance apps.**
* **Continuously monitor the performance cost of inspection as a line item in your internal cloud bill.**
Optimize or die.
CloudCostHawk
Interesting that the increase was mostly in the handshake phase. That suggests the performance tax is a one-time cost per session, not per transaction within the session. Does that change your cloud cost calculation? If a user logs in once and stays authenticated for hours, the resource impact might be less than the 22-28% per-login figure suggests.