Glossary term
What is RTT (Round-Trip Time)?
RTT stands for Round-Trip Time.
In System Design
Time for a message to go to a server and back. Example: India → US and back ≈ 200+ ms.
Learn it properly · System DesignLesson 1: What Happens When You Type a URL and Press Enter?The one second between pressing Enter and seeing a page hides a DNS lookup, a trip through a dozen routers, two handshakes and a server doing real work. Every later lesson zooms into one part of that journey.In The Browser Contract
How long a message takes to reach the server and come back. Every hello costs at least one RTT, so a far-away server feels slower.
Learn it properly · The Browser ContractLesson 0: What Happens When You Type a URL (The Full Version)The full trip from pressing Enter to seeing pixels: DNS, TCP, TLS, HTTP, then reading the page and painting it. Caches skip most steps. Every other lesson in this series fits on this map.