Warning: client_writable limitations and gotcha's

[owen.campbell]

@splinter

Do not use them in their current limited form for anything but throwaway, toy projects (and the knowledge of how they work/where they’re helpful is just a waste as well since you can’t actually use them for anything serious).

I couldn’t agree less. I regularly use them to upload data where an ordinary server call might lead to a timeout due to the payload size: Timeout on large file upload