Is REST V3 / GraphQL v4 query real-time?

I suspect that both are not real-time but somehow cached. 
Does anybody know? I can’t find this in the document.  

Let me elaborate a little bit: 
I have a service that subscribed to a repo’s webhook event. 
When a  push  event is coming in, I then query GitHub through REST V3 / GraphQL v4. 
To my surprise that the service failed to retrieve info from either REST or GraphQL (Get PR # from commitSHA). 
I then added a sleep(1s) in my service, this time it works. 

Thus lead to the question above. 

There is a similar case

Hi @louisluhao,

Thanks for writing in about this, I’m sharing the reply from our support team as it might be helpful to another user with a similar concern. In the meantime, we’re looking forward to seeing you around!

“API queries should be real time. However, it sounds like there was a required background job needed to update the merge_commit_sha and you happen to run the query before it was completed. Therefore you were unable to obtain the data, but when you added the sleep, the job was finished and gave you a response.”