A refreshing viewpoint: when we use UDP as an unreliable protocol, we often actually wants its "timeliness" property, which is to say if we have to choose from dropping two versions of a data, we want to drop the old one. This is why real-time video streaming and gaming choose UDP. The datagram extension in QUIC offers a nice solution. Data are split into streams, within each stream data is ordered. Each stream has a priority attached that is used to determine which packet to drop.

However, how do you choose which to drop without having a bloating buffer that hurts latency? The author suggests using delay-based congestion control like BBR that uses network metrics to probe the bandwidth and RTT.