real-time data sync: what's your go-to db strategy

hey all, i'm wrestling with a real-time data synchronization problem for a new app. we need changes to propagate across multiple client applications almost instantly. thinking about using something like Firebase Realtime Database or Supabase, but also curious if anyone has had success with more traditional relational databases with specific extensions or patterns for real-time updates. what are your battle-tested approaches for keeping data live across clients without blowing up the backend