Track map markers in a certain square without refresh
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I'm trying to find right (or the best) solution for following question:

Say, i have a google map (it's not matter actually what kind of map) where people can create and delete markers. Any user can look at the map and i know bounds of square which user looks now. So if somebody else creates marker on this square, i need to show it on the map immediatelly. For it i'm going to use websockets. But the question is not in a technical side but regarding to logic. What is the best way to send marker's data to user? Should i store somehow current bounds of showed location? I don't want to send new marker to all users because they may not need it, i want to send only to those who look at that square. Or i have to have producer who will be giving this information to consumers?

Sorry if i've written confusing stuff, ask me in case if something unclear. Thanks for your suggestions.