200 Milliseconds: An Interactive Trace of an HTTP Request's Full Lifecycle

“200 Milliseconds” is an interactive visualization rather than a written article. It follows a single HTTP request through the roughly 200-millisecond journey it takes from a client to a server and back, breaking down each layer the request passes through along the way.

The piece walks through the full stack involved in serving one request: DNS resolution, the TCP handshake, TLS negotiation, the operating-system kernel, Node.js’s event loop, and a Postgres database query. By making each of these normally-invisible steps observable, it illustrates how much coordinated work happens beneath a seemingly instantaneous web interaction.

For an engineering audience, the value is pedagogical: it maps where latency actually accumulates across the network and server pipeline, which is useful context for performance tuning and for reasoning about where optimization effort pays off. Note that because the source is a visual, interactive tool with essentially no body text, this summary describes the resource itself rather than condensing written prose.