Jake Walker Jake Walker - 1 month ago 8
Swift Question

How do I constantly check if something on a server (Parse) has changed without thousands of requests?

I am creating an application which has a follow mechanism where the followed user has to accept the request of a following (similar to private accounts on instagram).

I then want the following user to find out when the other user has checked a million times (every time the following user opens the screen if I did the query in viewDidLoad). However, the problem with this, is that there will be a lot requests which will expensive to me as I will have to pay for the requests to Parse so I want to minimise these queries.

Currently, the best thing I can think of is to check once a day at midnight for example but this doesn't seem very seamless.

Is there a better way of doing this?

Answer

For starters consider how stale you are willing to allow an app's view of the world to be and cache the response that long. If a user views that screen every 30 seconds you might only want to actually check with the server 5 minutes after the last successful response (or the last response which had 0 follow requests).

You might consider switching from this sort of "pull" polling where the client decides when to ask the server if anything has changed to a "push" model where the server can inform the client when a change occurs. For example you can send a silent background push notification to a user's devices when they have a follow request, the app can then respond by performing your existing query.

You might still want polling or user triggered requests (like a "pull to refresh" gesture) as a fallback for missed notifications or devices with notifications disabled but you should be able to drastically reduce request volume.