Also, as we do with most of our work, we open-sourced the server we are using to send these notifications. It accepts registration requests over web sockets like a relay and then listens to registered user’s relays for posts mentioning them. When it sees one it sends a silent background notification to the iOS app which can then download the events for itself and display the appropriate notifications. It’s a slick piece of engineering by nostr:npub1uucu5snurqze6enrdh06am432qftctdnehf8h8jv4hjs27nwstkshxatty. https://github.com/planetary-social/nos-notification-service-go