I Tested Every Change on a Throttled Connection for a Month. Three Problems Disappeared.

I used to test on fast wifi. Everything worked. Then I started throttling every test to slow 3G with occasional drops.

Three issues surfaced immediately. A loading state that never showed because the request was too fast to notice. A retry that fired twice on a slow connection. A button that stayed disabled after a failed request because the error handler didn't reset it.

None of these reproduced on a fast connection. All of them were real for someone on a train.

What's the environment you keep testing in that isn't the environment your users are in?