Continually send transaction logs from your master database to an S3 bucket and generate the reports off the S3 bucket using S3 byte range requests.
Generate the reports by querying the synchronously replicated standby RDS MySQL instance maintained through Multi-AZ.
Launch a RDS Read Replica connected to your Multi AZ master database and generate reports by querying the Read Replica.
Generate the reports by querying the ElastiCache database caching tier.
Explanations:
Continuously sending transaction logs to S3 and generating reports from there is not efficient for real-time reporting. It adds latency and requires additional processing, making it unsuitable for aggregating user-generated data every 30 minutes.
Querying the synchronously replicated standby RDS MySQL instance may introduce latency and could still impact the primary database performance. The standby is not intended for read operations and using it for reporting could lead to performance degradation.
Launching a RDS Read Replica allows for offloading read queries from the primary database. The Read Replica can handle the reporting workload without affecting the performance of the master instance, making it the best option for generating reports efficiently.
ElastiCache is primarily a caching layer and does not store the complete data necessary for generating reports. Querying it would lead to incomplete or inaccurate reports as it does not persist data in the same way as the database.
My best guess is:
Launch a RDS Read Replica connected to your Multi AZ master database and generate reports by querying the Read Replica.