From the documentation:
Eventually consistent: When you request information about a user (or a group of users), the response might not reflect the results of a recently-complete write operation. However, if you repeat your request after a short period of time, the response will return up-to-date data.
Have in mind that the short period of time mentioned is under normal circumstances; peaks in system usage may result in increased delays and longer ones can also happen if there’s something abnormal happening, however, these longer delays would be reported through the status page.
The important part is that the results are not immediately consistent and your application should take that under consideration. If you just created a user you will have its user identifier so in general there should be no need to immediately search for that user given you can obtain its information by user identifier.