TL;DR — Twitter Direct Messages

Design the Direct Messages feature for Twitter/X that supports 1-on-1 and group conversations at scale. Users should be able to send text messages, share media (photos, videos, GIFs), react to messages with emojis, and receive messages in real time even across multiple devices (phone, tablet, web). Key features: Send text messages in 1-on-1 and group DMs (up to 50 members). Share media: photos, videos, GIFs, links with previews.