It definitely isn't easy, but it's the kind of challenges we love! You mentioned many of the big ones, but there's also just the sheer scale of the userbase, which means the libraries will be run under every permutation of runtime and configuration under the sun. It's a lot of edge cases to get right!
Their team is great to work with, which helps make it worth it.
(Note that a lot of the SSE type stuff we do generally so we're able to support a variety of AI companies and other streaming use cases, though disclaimer it is a premium feature)