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.

qwiki labs AWS Solution Architect Quest

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.

Attaching IAM role to a running EC2 instance

The focus areas/domains of the exam would be:

  1. Designing highly available, cost-efficient, fault-tolerant, scalable systems 60%
  2. Implementation/Deployment 10%
  3. Data Security 20%
  4. Troubleshooting 10%

Good Luck!!