Measure LLM Streaming TTFT and E2EL in C#: A Beginner’s Hands-On Guide
Start a monotonic timer just before sending the request, record the first non-empty generated-text event, and keep the last-text timestamp separate from the completion signal. This guide shows the distinction in a runnable C# streaming lab. What was actually tested? C# code over real loopback HTTP, using a simulated SSE generator. No actual LLM was called. No model, provider, GPU, token count or paid inference performance was measured. Environment checked: 2026-10-16 · Windows build 10.0.26200 x64 · .NET SDK 10.0.400 · .NET runtime 10.0.11. Other operating systems and .NET versions were not executed for this article. 1. Definitions first: what will we measure? Token: a model’s processing unit. It is not necessarily a word, character, HTTP chunk or SSE event. TTFT — Time to First Token: wait from a defined request start to the first generated output token at the measurement point. This text client uses the first non-empty generated-text event as a proxy , not a token-generation time...