I took the Developer Associate last Friday and successfully passed the exam. I studied for about 2 months 3 hours per day.
A little background I've been using AWS for almost 4 years now, I am working heavily with EC2, VPC, S3 and RDS daily at work. Having the experience in AWS helped but is not enough to pass the certs you need to broaden your knowledge took some courses because there are many stuffs to learn.
The questions that I've got are heavily focused on serverless, Lambda, API Gateway, Cognito, Elastic Beanstalk, ECS/ECR, Cloudfront, S3, EC2, Kinesis, DynamoDB and IAM and its relationships with all services. Aside from this there are few questions on Codebuild, Codedeploy and X-ray.