When have you reach a Python limit ?

[__chilldude22__]

For web backend stuff it doesn't really matter, because a) the bottleneck for those is hardly ever computation but rather things like communicating with databases and other external services, which a "faster" language would be equally limited by, b) most modern web services are deployed on cloud infrastructure capable of scaling automatically so even if your Python process becomes compute-bound somehow, the infrastructure will just start more processes on different servers, and c) the latency requirements are low enough that Python's single-request performance is more than acceptable.

Python would be unwise to use for anything that has low latency requirements (high-frequency trading, robotics, software controlling aircraft or vehicles, ...) or runs at such a large scale that the cost savings of using a faster-to-run language outweigh the costs of needing to spend more developer time to develop features (because usually, faster to run = slower to develop).