Add marker with time validity and near real time
<p>In my asp.net web api application with angularJS frontend I want to display marker on a map (google maps or leaflet) with time validity in near real time. </p>

<p>What is that meaning? </p>

<ol>
<li>Each user (client) of the app should immediately (near real time) see when
another user add a marker on the map.</li>
<li>Each added marker can have a different time validity. So if the time
validity is expired, the marker should be removed from the map and
each user should see that.</li>
</ol>

<p>There are two options to do that - client side or server side.
On client side there are "timer" available for each marker (e.g. <code>.setTimeout()</code>). But if I have hundreds of markers with different time validity, I would need the same number of timer. Would that not need to much ressources on client side? So I thought it would be better to do this on server side? If the time validity is expired of a marker, I want to remove that marker from each client. But that would mean, that I have to send request for each marker. Is there any best practice to do that? Maybe with SignalR or something like that?</p>