The Azure AZ-305 exam is one of the two exams required to earn the Microsoft Certified: Azure Solutions Architect Expert certification. The other exam is AZ-104: Microsoft Azure Administrator.
The AZ-305 exam does not have any official pre-requisites, meaning you can take it without passing any other exam first. However, even if you pass the AZ-305 exam, you will not earn the certification until you also pass the AZ-104 exam. Therefore, it is recommended that you take the AZ-104 exam before the AZ-305 exam, as it covers the basic Azure administration skills that are necessary for the AZ-305 exam.