⚡Delivery Hero Cuts Home Screen Latency 17% by Moving Apps to HTTP/3

Your mobile API latency problem might have a protocol fix

Delivery Hero just proved that swapping transport protocols can beat most backend optimizations. The food delivery giant moved 95 percent of its users to HTTP/3 and cut total end-to-end response time on its home screen by 17 percent. Not bad for a config change. If you ship a mobile app, this one is for you. The protocol replaces TCP with QUIC over UDP, which kills a lot of the handshake overhead and stops one lost packet from stalling the whole stream. Delivery Hero's team also used session tickets and QUIC's 0-RTT to start sending data before the handshake finished. Setup was surprisingly easy on iOS, since Apple has supported HTTP/3 since iOS 15. Android needed Google's Cronet library, and the team used OKCronet to avoid rewriting their existing networking code. The numbers are the reason to read the full case. P95 latency dropped from 1.2 seconds to 120 milliseconds, a 10x improvement in read latency. Handshake latency fell 51 percent, and response time in Pakistan was cut in half. Devices on networks that block UDP automatically fell back to HTTP/2, so nothing broke for them. The catch? Secondary screens still have latency problems in markets prone to packet loss. Delivery Hero is working with Cloudflare on a congestion algorithm issue, so expect that fix to be the next chapter.