Here is a list of materials to help you to prepare for AWS Solution Architect exams:
A curated list of AWS resources to prepare for the AWS Certifications https://gist.github.com/leonardofed/bbf6459ad154ad5215d354f3825435dc
AWS Whitepapers - (must read) https://aws.amazon.com/whitepapers/
AWS Youtube channel has a great set of resources. Here is a playlist - https://www.youtube.com/playlist?list=PLhr1KZpdzukcMmx04RbtWuQ0yYOp1vQi4
If you have attended to the AWS SA Training, you need to read Architecting on AWS Student Guide which is 780 pages.
Also, acloud.guru has a great set of online courses that also could be purchased via udemy https://www.udemy.com/aws-certified-solutions-architect-associate/learn/v4/overview
I think most important thing is also to experience the AWS services yourself rather than just reading the materials provided.
You can also try the AWS labs at https://qwiklabs.com/. Find the quest for AWS Solution Architect. It has a good set of exercises. There are also free labs that you can try and experience AWS services without having an AWS account.
AWS platform is a very dynamic platform and it changes all the time with more awesome features and new services.
To give you a specific example, 2016 Q4 you couldn't attach IAM role to an already created EC2 instance, however, today you can attach an IAM role to an EC2 instance.
The focus areas/domains of the exam would be:
- Designing highly available, cost-efficient, fault-tolerant, scalable systems 60%
- Implementation/Deployment 10%
- Data Security 20%
- Troubleshooting 10%