Azure Solutions Architect Expert certification mainly focuses on compute, network, storage, and security. I recommend getting the Azure Administrator Associate & Azure Security Engineer Associate before pursuing the Solutions Architect certification, and the below document outlines the Solutions Architect certification journey.
Azure-Solutions-Architect-certification-journeyMicrosoft Azure Architect Technologies (beta)
Exam AZ -303
Microsoft Azure Architect Design (beta)
Exam AZ – 304
Skills Outline Guide
AZ-303
AZ-304
Learning Path
Microsoft Azure Well-Architected Framework
Architect network infrastructure in Azure
Architect storage infrastructure in Azure
Architect compute infrastructure in Azure
Architect infrastructure operations in Azure
Architect a data platform in Azure
Architect infrastructure operations in Azure
Architect migration, business continuity, and disaster recovery
Architect modern applications in Azure
Architect secure infrastructure in Azure
Additional Resources
Azure Architecture Center
Microsoft Docs