Hello Ke!
Thank you for contacting Microsoft's Community.
Based on your inquiry, we understand that you have inquiries about the Pathway for the Microsoft Certified: DevOps Engineer Expert Certification. We will be happy to help you.
Your AZ-400 certification will not be valid for 2 years. Microsoft role-based and specialty certifications are valid for 1 year from the date you cleared the certification exam and completed the prerequisite.
Please bear in mind that the Exam AZ-400: Designing and Implementing Microsoft DevOps Solutions - Certifications | Microsoft Learn is one of the conditions to obtain the Microsoft 365 Certified: Administrator Expert Certification as shown in the image below:

Keep in mind that the AZ-400 Exam does not issue a Certification by itself.
The available requisites for the Microsoft Certified: DevOps Engineer Expert - Certifications | Microsoft Learn, are the following for your reference:
In summary you need to pass Exam AZ-400: Designing and Implementing Microsoft DevOps Solutions (As yo do) and earn either the Azure Administrator Associate or the Azure Developer Associate.
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