During concurrency, requests are unusually slow

[murongqingsi]

I created an API, and the logic within this API requires calling a third-party interface to obtain data. However, when using JMeter for stress testing, the concurrency is only in the single digits or a dozen. It can't even reach 50, which indicates poor performance. If I directly call the third-party interface, the concurrency is very high. What could be the reason for this?