This is the notes I prepared while studying and researching for AWS Big Data certification. I intend to make it more user-friendly with additional notes one day.
My two cents: To know every topic in the exam deeply enough is a long shot. This is a 3-hour 300 dollar exam (might change in future, Amazon just introduced this certification program). But if you know two or three areas deeply (and decent knowledge about all data platforms on AWS) it should balance out the complicated exam questions from less-known areas. I had a deep interest in Redshift and DynamoDB, so that saved me.
If you're preparing for AWS Big Data Specialty, best wishes from me!