load-testing-overview

Load testing drives concurrent, sustained traffic at a deployed system and measures what happens to response time, throughput, and errors while that traffic runs. It assumes correctness and asks whether the system stays fast and correct under load, and where it stops being either. It needs a deployed environment, realistic data volumes, and a real network path; run one against a laptop dev server and you measured the laptop.

Pick a tool from what is already in the repo

Five tools cover almost every case. Read the table top to bottom and stop at the first row that is true of your project. The rows are ordered so that hard constraints (protocol, who authors the tests) beat preferences (language).