See practical search performance guide. The guide walks through a music search use case and gives a practical introduction to Vespa search performance.
Sizing and capacity planning involves figuring out how many nodes are needed and what kind of hardware flavor best fits the use case:
Benchmarking is important both during sizing and for testing new features. What tools to use for benchmarking and how to tune system aspects of Vespa:
Do a deep performance analysis - how to profile the application as well as Vespa: