Learn about the Flow REST API asynchronous request-response model.
The REST API works asynchronously. Unlike other NLP APIs, it will not return a direct reply to a send message request.
Need a synchronous response?
See the Synchronous responses guide to learn about an optional synchronous reply mode supported by certain endpoints.
The below images represent the request-response model.
![Screenshot 2021-09-30 at 4.04.29 PM.png 2518](https://files.readme.io/8337156-Screenshot_2021-09-30_at_4.04.29_PM.png)
Sending a message to Khoros Flow
![Screenshot 2021-09-30 at 4.06.03 PM.png 2524](https://files.readme.io/1ca29e3-Screenshot_2021-09-30_at_4.06.03_PM.png)
Receiving replies from Khoros Flow
Instead, the API will respond by sending a POST request to your configured webhook url whenever an event takes place.