A company migrated one of its business-critical database workloads to an Amazon Aurora Multi-AZ DB cluster. The company requires a very low RTO and needs to improve the application recovery time after database failovers.
Which approach meets these requirements?

1. A. Set the max_connections parameter to 16,000 in the instance-level parameter group.
2. B. Modify the client connection timeout to 300 seconds.
3. C. Create an Amazon RDS Proxy database proxy and update client connections to point to the proxy endpoint.
4. D. Enable the query cache at the instance level.

Correct Answer: C
Amazon RDS Proxy allows applications to pool and share connections established with the database, improving database efficiency and application scalability. With RDS Proxy, failover times for Aurora and RDS databases are reduced by up to 66% and database credentials, authentication, and access can be managed through integration with AWS Secrets Manager and AWS Identity and Access Management (IAM).
https://aws.amazon.com/rds/proxy/

A database professional maintains a fleet of Amazon RDS database instances that are configured to utilize the default database parameter group. A database expert must connect a custom parameter group with certain database instances.
When will the instances be allocated to this new parameter group once the database specialist performs this change?

1. A. Instantaneously after the change is made to the parameter group
2. B. In the next scheduled maintenance window of the DB instances
3. C. After the DB instances are manually rebooted
4. D. Within 24 hours after the change is made to the parameter group

Correct Answer: C
When you associate a new DB parameter group with a DB instance, the modified static and dynamic parameters are applied only after the DB instance is rebooted.

A database specialist is working on an Amazon RDS for PostgreSQL DB instance that is experiencing application performance issues due to the addition of new workloads. The database has 5 ¢’ of storage space with Provisioned IOPS. Amazon CloudWatch metrics show that the average disk queue depth is greater than 200 and that the disk I/O response time is significantly higher than usual.
What should the database specialist do to improve the performance of the application immediately?

1. A. Increase the Provisioned IOPS rate on the storage.
2. B. Increase the available storage space.
3. C. Use General Purpose SSD (gp2) storage with burst credits.
4. D. Create a read replica to offload Read IOPS from the DB instance.

Correct Answer: A

A Database Specialist is troubleshooting an application connection failure on an Amazon Aurora DB cluster with multiple Aurora Replicas that had been running with no issues for the past 2 months. The connection failure lasted for 5 minutes and corrected itself after that. The Database Specialist reviewed the Amazon RDS events and determined a failover event occurred at that time. The failover process took around 15 seconds to complete.
What is the MOST likely cause of the 5-minute connection outage?

1. A. After a database crash, Aurora needed to replay the redo log from the last database checkpoint
2. B. The client-side application is caching the DNS data and its TTL is set too high
3. C. After failover, the Aurora DB cluster needs time to warm up before accepting client connections
4. D. There were no active Aurora Replicas in the Aurora DB cluster

Correct Answer: B
When your application tries to establish a connection after a failover, the new Aurora PostgreSQL writer will be a previous reader, which can be found using the Aurora read only endpoint before DNS updates have fully propagated. Setting the java DNS TTL to a low value helps cycle between reader nodes on subsequent connection attempts.
Amazon Aurora is designed to recover from a crash almost instantaneously and continue to serve your application data. Unlike other databases, after a crash Amazon Aurora does not need to replay the redo log from the last database checkpoint before making the database available for operations. Amazon Aurora performs crash recovery asynchronously on parallel threads, so your database is open and available immediately after a crash. Because the storage is organized in many small segments, each with its own redo log, the underlying storage can replay redo records on demand in parallel and asynchronously as part of a disk read after a crash. This approach reduces database restart times to less than 60 seconds in most cases

A business's mission-critical production workload is being operated on a 500 GB Amazon Aurora MySQL DB cluster. A database engineer must migrate the workload without causing data loss to a new Amazon Aurora Serverless MySQL DB cluster.
Which approach will result in the LEAST amount of downtime and the LEAST amount of application impact?

1. A. Modify the existing DB cluster and update the Aurora configuration to Serverless.
2. B. Create a snapshot of the existing DB cluster and restore it to a new Aurora Serverless DB cluster.
3. C. Create an Aurora Serverless replica from the existing DB cluster and promote it to primary when the replica lag is minimal.
4. D. Replicate the data between the existing DB cluster and a new Aurora Serverless DB cluster by using AWS Database Migration Service (AWS DMS) with change data capture (CDC) enabled.

Correct Answer: D
https://medium.com/@souri29/how-to-migrate-from-amazon-rds-aurora-or-mysql-to-amazon-aurora-serverless