Took my exam and passed it with charm. That was possible because of good learning material provided by Whizlabs practice exam with very detailed explanation. Another factor, I would say that i took SysOps first followed by SA associate before taking Deveoper Associate. CDA is the easiest or (will become) easier if you get prepared for other 2 first. Most of the syllabus is common and hence you left very few topics to learn more in depth. Focus on DynamoDB, RDS, ElastiCache. Bottom-line, Whizlabas practice exams (alone) can help you to pass this exam.