From your documentation:
Ensure HTTP Keep-Alive connections are enabled on your origin. Cloudflare reuses open TCP connections for up to 15 minutes (900 seconds) after the last HTTP request.
General best practices for load balancing at your origin with Cloudflare – Cloudflare Help Center
Does that mean that you use the same connection (between CF and the origin load balancer) for multiple users?
Or you only reuse the connection for multiple requests of the same user (if their browser asks for keep-alive)?