What is the acceptable HTTP request-response delay? I have a client-server application that takes 0.4 milliseconds as request-response delay. is this delay acceptable according to the standard?, knowing that there is no distance between the client and the server. please help
The admissible delay usually depends on your specific end users requirements, on how the application is going to be used. Only you, or the person that asked you to develop the application, can answer that question.
0.4 milliseconds looks like a very small and very good delay. But it all depends on the context where it is going to be used. If, for example, 100.000 requests needs to be done to actually do something useful with your application, then it will probably not be a very good user experience. Also, take care of how the delay might be changing if simultaneous requests needs to be served at the same time.
There is no such thing a the standard when it comes to HTTP delay. This standard is different for each application and end user context.