DBS-C01 Mock Exam 72 — 25 Questions

Question 1

A gaming company uses an Amazon ElastiCache for Redis cluster to store leaderboard data. The cluster is deployed in a single Availability Zone with cluster mode disabled. The company wants to improve read scalability and ensure high availability with automatic failover. The application uses the Redis cluster's primary endpoint for both reads and writes. Which configuration change should a database specialist make to meet these requirements with minimal application changes?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

Create a Redis replication group with one primary and multiple read replicas, and enable Multi-AZ with automatic failover.. Creating a Redis replication group with read replicas and enabling Multi-AZ automatic failover provides read scalability by allowing the application to direct read traffic to replicas via the reader endpoint, while writes go to the primary endpoint. Multi-AZ ensures high availability with automatic failover. The application only needs to use the reader endpoint for reads, which is a minimal change.

Answer

Use ElastiCache for Redis with a single shard and enable encryption in transit.

Answer

Migrate to Amazon DynamoDB with global secondary indexes for leaderboard queries.

Answer

Enable cluster mode and use the configuration endpoint for all operations.

Question 2

A database specialist manages an Amazon Aurora PostgreSQL DB cluster. Users report that queries against a reader instance intermittently return stale data that is several seconds behind the writer. The specialist wants to quantify this lag over time and identify whether it correlates with writer activity. Which AWS mechanism should the specialist use to obtain this information?

Accepted Answer

Enable Aurora Replica lag monitoring by publishing the AmazonAuroraReplicaLag metric from the DB cluster to Amazon CloudWatch.. Aurora publishes AmazonAuroraReplicaLag in milliseconds for each Aurora Replica to CloudWatch. Graphing that metric over time is the supported way to quantify how far behind a reader is and to correlate lag with writer activity. The other mechanisms either report unrelated performance data or rely on PostgreSQL streaming-replication views that do not reflect Aurora storage-level replication.

Answer

Query the pg_stat_replication view on the writer instance to read the replay_lag column for each connected replica.

Answer

Enable Performance Insights on the reader instance and inspect the db.sql.statement metric for delayed queries.

Answer

Enable Enhanced Monitoring on the DB cluster and read the replica_lag metric from the OS-level process list.

Question 3

A company uses Amazon DynamoDB to store user session data. The security team wants to ensure that all data stored in the table is encrypted at rest using a customer-managed AWS KMS key so they can control key rotation and audit key usage. The table currently uses the AWS owned key. What should a database specialist do to meet this requirement?

Accepted Answer

Create a new table with the customer-managed KMS key specified, migrate the data, and update applications to use the new table.. DynamoDB tables are encrypted at rest by default, but the encryption key choice is made at creation and cannot be changed afterward. To use a customer-managed KMS key, you must create a new table with that key and migrate data into it. Resource policies and KMS grants manage access, not the table's encryption key binding.

Answer

Enable AWS KMS customer-managed key encryption by adding a resource-based policy to the existing table that references the KMS key.

Answer

Modify the table's encryption settings in the DynamoDB console to select the customer-managed KMS key.

Answer

Use AWS KMS grants to associate the customer-managed key with the existing table's underlying storage.

Question 4

A company is migrating an on-premises Oracle database to Amazon RDS for Oracle. The database uses a non-standard character set that is not supported by RDS for Oracle. The migration must preserve the data with minimal transformation. Which approach should the company take?

Accepted Answer

Convert the source database to a supported character set before migration, then use native tools or AWS DMS to migrate.. RDS for Oracle supports only a specific list of character sets. When the source uses an unsupported character set, the only viable approach is to convert the source database to a supported character set before migration. This ensures that the target DB instance can store the data correctly. After conversion, standard migration tools like Oracle Data Pump or AWS DMS can be used. Creating an instance with an unsupported character set is not possible.

Answer

Use Oracle GoldenGate to replicate data to RDS for Oracle, which will automatically map the character set.

Answer

Create an RDS for Oracle DB instance with the same non-standard character set using a custom parameter group.

Answer

Use AWS DMS to migrate the data to RDS for Oracle, specifying the target character set as the default.

Question 5

A company is deploying an Amazon DynamoDB table for a new application. The table will store session data with a TTL attribute. The company wants to ensure that expired items are automatically deleted and that the deletion does not consume write capacity. Which configuration should they use?

Accepted Answer

Enable TTL on the table and specify the TTL attribute name.. DynamoDB TTL automatically deletes expired items without consuming write capacity. It is a native feature that requires enabling TTL and specifying the attribute. Other methods involve manual or triggered deletions that consume capacity.

Answer

Enable DynamoDB Accelerator (DAX) and configure TTL on the DAX cluster.

Answer

Create a global secondary index (GSI) on the TTL attribute and query for expired items to delete them.

Answer

Use a DynamoDB Streams trigger to delete expired items with a Lambda function.

Question 6

A database specialist needs to monitor the number of write capacity units consumed by an Amazon DynamoDB table. The specialist wants to receive an alert when the consumed write capacity exceeds 80% of the provisioned capacity for 5 consecutive minutes. What should the specialist do?

Accepted Answer

Create an Amazon CloudWatch alarm on the ConsumedWriteCapacityUnits metric with a threshold equal to 80% of the provisioned capacity, a period of 1 minute, and 5 evaluation periods, then configure an Amazon SNS topic for notifications.. The ConsumedWriteCapacityUnits metric is the correct choice for monitoring write capacity consumption. To alert when consumption exceeds 80% of provisioned capacity for 5 consecutive minutes, set the alarm period to 1 minute and evaluation periods to 5. This ensures the alarm triggers only if each of the 5 minutes exceeds the threshold. The threshold should be 80% of the provisioned write capacity units. Using Amazon SNS for notifications completes the solution.

Answer

Create an Amazon CloudWatch alarm on the WriteThrottleEvents metric with a threshold of 80% of the provisioned capacity and a period of 5 minutes, then configure an Amazon SNS topic for notifications.

Answer

Enable DynamoDB Streams on the table and use an AWS Lambda function to calculate the consumed write capacity, then publish a custom metric to Amazon CloudWatch and create an alarm.

Answer

Create an Amazon CloudWatch alarm on the ConsumedWriteCapacityUnits metric with a threshold of 80% of the provisioned capacity and a period of 5 minutes, then configure an Amazon SNS topic for notifications.

Question 7

A database specialist must grant an application running on Amazon EC2 permission to call the rds:CreateDBSnapshot and rds:DescribeDBSnapshots API actions on a specific Amazon RDS for MySQL DB instance only, using temporary credentials. The application must not be able to modify or delete any DB instance. Which combination of steps should the specialist take to meet these requirements with least privilege?

Accepted Answer

Create an IAM role with a trust policy for ec2.amazonaws.com, attach an IAM policy that allows rds:CreateDBSnapshot and rds:DescribeDBSnapshots with a resource ARN scoped to the specific DB instance, and attach the role to an instance profile on the EC2 instance.. Temporary credentials for EC2 workloads come from an IAM role attached via an instance profile, which the instance metadata service vends automatically. Least privilege requires the policy to allow only rds:CreateDBSnapshot and rds:DescribeDBSnapshots and to scope the resource to the specific DB instance ARN. No broader actions or wildcard resources should be included, and the trust policy must allow ec2.amazonaws.com to assume the role.

Answer

Attach the AWS managed policy AmazonRDSFullAccess to an IAM role used by the EC2 instance so the application can perform snapshot operations and any future RDS tasks it may need.

Answer

Create an IAM role with a trust policy for rds.amazonaws.com, attach an inline policy allowing rds:CreateDBSnapshot and rds:DescribeDBSnapshots on all resources, and configure the EC2 instance to assume the role at boot.

Answer

Create an IAM user, generate an access key and secret access key, store them in AWS Systems Manager Parameter Store, and have the application retrieve them at startup to call the RDS APIs.

Question 8

A media company runs an Amazon Neptune cluster for a social graph. The workload is read-heavy with occasional bursts of writes. The company needs to minimize read latency during peak hours and must ensure that reads are served by replicas to offload the primary. Which endpoint should the application use for read queries, and which feature must be enabled to ensure replicas are used?

Accepted Answer

Use the reader endpoint and ensure that at least one replica exists in the cluster.. Amazon Neptune provides a reader endpoint that load-balances read-only queries across all replicas in the cluster, reducing load on the primary and improving read latency. For the reader endpoint to route to replicas, the cluster must have at least one replica; otherwise it falls back to the primary. Using the reader endpoint with at least one replica meets the read-heavy requirement.

Answer

Use the instance endpoint of the primary and enable read replicas with automatic failover.

Answer

Use the cluster endpoint and enable reader endpoint routing.

Answer

Use the reader endpoint and enable Neptune Streams to replicate reads.

Question 9

A company is deploying a new Amazon RDS for PostgreSQL database for a development environment. The team wants to minimize costs and does not require high availability or read replicas. The database can tolerate brief interruptions. Which RDS feature should they use?

Accepted Answer

Single-AZ deployment. For a development environment that does not require high availability or read scaling, a Single-AZ deployment is the most cost-effective option. Multi-AZ adds a standby for failover, read replicas add read capacity, and Aurora Global Database is for cross-Region Aurora deployments. None of those are needed here, and all increase cost. Single-AZ aligns with the stated tolerance for brief interruptions and minimal budget.

Answer

Read replica in a second Availability Zone

Answer

Aurora Global Database

Answer

Multi-AZ deployment

Question 10

A database specialist is troubleshooting an Amazon RDS for MySQL DB instance that has been experiencing sudden performance degradation. The specialist suspects that a recent schema change or query pattern is causing excessive temporary table usage on disk. Which CloudWatch metric should be examined to identify the number of temporary tables created on disk?

Accepted Answer

CreatedTmpDiskTables. CreatedTmpDiskTables is the CloudWatch metric that specifically tracks the number of internal on-disk temporary tables created by the MySQL server. When queries require temporary tables that exceed the configured in-memory limit (tmp_table_size and max_heap_table_size), MySQL creates them on disk, causing I/O overhead and performance degradation. Monitoring this metric helps the specialist confirm whether disk-based temporary tables are the root cause of the slowdown.

Answer

CreatedTmpTables

Answer

TmpTableSize

Answer

InnodbBufferPoolHitRate

Question 11

A financial analytics firm stores trade records in an Amazon Redshift cluster. Analysts run complex joins and aggregations over several years of data, and queries frequently scan large fact tables. The team wants to reduce query runtimes and storage cost without changing the SQL or the table structure. Which action should a database specialist take?

Accepted Answer

Enable automatic table optimization so Redshift chooses sort and distribution keys and applies compression encodings.. Automatic table optimization lets Redshift tune sort keys, distribution keys, and compression encodings based on observed query patterns. Effective sort keys allow block-level pruning so scans read less data, and compression shrinks the stored footprint. Because it acts on existing tables without requiring SQL or schema changes, it reduces both query runtime and storage cost, matching the firm's requirements.

Answer

Increase the number of nodes in the cluster to add more compute and storage capacity.

Answer

Enable Redshift concurrency scaling to add transient clusters during peak query periods.

Answer

Apply Redshift Spectrum to query the fact tables directly from Amazon S3.

Question 12

A financial services company runs an Amazon Aurora PostgreSQL cluster. The security team must ensure that all connections to the database use TLS and that the database rejects any unencrypted connections. The team has already obtained the rds-ca-2019 certificate and configured the client applications to use SSL. Which additional step is required to enforce TLS for all connections?

Accepted Answer

Set the rds.force_ssl parameter to 1 in a custom DB cluster parameter group and apply it to the cluster.. The rds.force_ssl parameter in Aurora PostgreSQL enforces SSL/TLS for all connections. Setting it to 1 in a custom cluster parameter group and associating it with the cluster ensures that any non-SSL connection attempt is rejected. This is the standard method to require encryption in transit. Other options address authentication, network filtering, or encryption at rest, none of which enforce TLS on connections.

Answer

Enable encryption at rest using an AWS KMS customer managed key for the DB cluster.

Answer

Modify the DB cluster to enable IAM database authentication and require all users to authenticate with IAM credentials.

Answer

Attach a security group to the DB cluster that only allows inbound traffic on port 5432 from IP addresses that support TLS.

Question 13

An e-commerce company uses Amazon ElastiCache for Redis to cache product catalog pages. The catalog is updated nightly in a batch job, and the team wants the cache to reflect the new data immediately after the batch completes without waiting for TTL expiration. The team wants a simple, low-effort approach that avoids stale reads. Which approach should the team use?

Accepted Answer

Invalidate or overwrite the affected cache keys as part of the batch job completion.. Explicitly invalidating or overwriting the affected keys at batch completion is the simplest way to ensure the cache reflects the new catalog immediately. It avoids the stale-read window and hit-ratio penalty of TTL-based expiry and does not require changing the cluster topology. Cluster mode and Multi-AZ address scalability and availability rather than cache coherence.

Answer

Enable Multi-AZ with automatic failover on the ElastiCache for Redis cluster.

Answer

Set a very short TTL on all cached catalog keys so entries expire quickly after the batch.

Answer

Enable cluster mode on the ElastiCache for Redis cluster to distribute the catalog keys.

Question 14

A database specialist is troubleshooting an Amazon Aurora MySQL DB cluster that is experiencing high write latency. The specialist suspects that the issue is related to the Aurora storage subsystem. Which two actions should the specialist take to monitor and diagnose the storage-related performance? (Choose two.)

Accepted Answer

Use Amazon RDS Performance Insights to analyze DB load by wait events, specifically io/aurora_redo_log_flush.. VolumeReadTime and VolumeWriteTime provide direct measurements of Aurora storage latency, while Performance Insights wait events like io/aurora_redo_log_flush reveal storage-related waits at the database level. Together, they help diagnose whether write latency stems from the Aurora storage subsystem. Other options focus on auditing, local storage, or instance-level metrics, which are less relevant.

Answer

Monitor the FreeLocalStorage metric in CloudWatch to ensure the instance has enough local storage for writes.

Answer

Enable Enhanced Monitoring to view disk I/O metrics at the instance level.

Answer

Enable Aurora Advanced Auditing and analyze the audit logs for slow write queries.

Question 15

A company uses Amazon Aurora PostgreSQL and wants to implement row-level security (RLS) to restrict access to rows based on the current database user. The security team requires that the RLS policies are enforced for all users, including the table owner, and that the policies are applied automatically when new tables are created in a specific schema. Which combination of actions should a database specialist take to meet these requirements?

Accepted Answer

For each table, enable RLS with ALTER TABLE ... ENABLE ROW LEVEL SECURITY, then use ALTER TABLE ... FORCE ROW LEVEL SECURITY, and create policies using CREATE POLICY. To automate for new tables, create an event trigger that executes these commands on table creation.. To enforce RLS for all users including the table owner in Aurora PostgreSQL, you must enable RLS on each table and then use FORCE ROW LEVEL SECURITY. This ensures that the table owner is also subject to the policies. Policies are created with CREATE POLICY to define row access. To apply this automatically to new tables in a schema, an event trigger can be set up to execute the necessary ALTER TABLE and CREATE POLICY commands upon table creation. This combination satisfies the requirement for automatic enforcement.

Answer

Create a role with BYPASSRLS privilege, grant it to all users, and create RLS policies that reference the current_user.

Answer

Create a view for each table that filters rows based on current_user, grant SELECT on the views to users, and revoke direct table access.

Answer

Enable RLS on each table using ALTER TABLE ... ENABLE ROW LEVEL SECURITY, create policies with CREATE POLICY, and set the row_security parameter to on for all users.

Question 16

A database specialist is deploying an Amazon RDS for PostgreSQL DB instance in a production environment. The company requires that the database be highly available and automatically fail over to a standby in case of an availability zone outage. The specialist enables Multi-AZ deployment. Which statement accurately describes the behavior of the standby instance in this configuration?

Accepted Answer

The standby instance is in a different Availability Zone and is synchronously replicated.. In an Amazon RDS Multi-AZ deployment, the standby instance is created in a different Availability Zone and receives synchronous updates from the primary. This ensures high durability and enables automatic failover with no data loss. The standby is not accessible for read or write operations; it exists solely for failover. Other options incorrectly describe the standby's role or replication method.

Answer

The standby instance is in the same Availability Zone and uses asynchronous replication.

Answer

The standby instance serves read-only traffic to offload the primary.

Answer

The standby instance can be promoted to a read replica to improve read scalability.

Question 17

A financial services company is building a new application that requires a relational database with ACID compliance and the ability to scale reads across multiple Availability Zones. The application must also support automatic failover with minimal downtime. The company wants to minimize operational overhead and does not want to manage database software. Which AWS service should a database specialist recommend?

Accepted Answer

Amazon Aurora MySQL with a writer and multiple reader instances across Availability Zones. Aurora MySQL provides a fully managed relational database with ACID compliance, multi-AZ durability, and the ability to add reader instances across AZs for read scaling. Failover to a reader is automatic and fast, minimizing downtime. RDS for MySQL Multi-AZ does not serve reads from the standby, DynamoDB is not relational, and Redshift is for analytics, so Aurora is the best fit.

Answer

Amazon Redshift with a multi-node cluster

Answer

Amazon DynamoDB with global tables enabled

Answer

Amazon RDS for MySQL with a Multi-AZ deployment

Question 18

A company is migrating a 10 TB on-premises Oracle database to Amazon RDS for Oracle. The network link to AWS is 100 Mbps. The database must remain fully operational during the migration, and the cutover must complete within a 30-minute window. Which migration strategy should be used?

Accepted Answer

Use AWS Database Migration Service (AWS DMS) with ongoing replication, then perform a cutover after the replication lag reaches zero.. For a large, live database migration over a slow network with a tight cutover window, AWS DMS with ongoing replication is the correct choice. It performs an initial full load and then continuously applies source changes to the target. Once replication lag is near zero, you can stop writes at the source, let DMS catch up, and promote the target within minutes. Other methods either require downtime or do not support continuous synchronization.

Answer

Use AWS Database Migration Service (AWS DMS) with full load only, scheduling the migration during a maintenance window to minimize impact.

Answer

Use Oracle Data Pump to export the database to an Amazon S3 bucket, then use AWS DMS to load the dump files into Amazon RDS for Oracle.

Answer

Use AWS Snowball Edge to transfer a physical backup of the database to AWS, then restore it to Amazon RDS for Oracle.

Question 19

A company is migrating its on-premises MySQL database to Amazon Aurora MySQL. The database is 1 TB and has a high write workload. The company wants to minimize downtime and ensure data consistency. They plan to use AWS DMS. During testing, they notice that the replication instance is experiencing high CPU utilization and the migration is slower than expected. Which action should they take to improve performance?

Accepted Answer

Increase the size of the replication instance to a larger instance class.. High CPU utilization on the AWS DMS replication instance during a migration indicates that the instance lacks sufficient resources. Scaling up to a larger instance class provides more CPU and memory, directly addressing the bottleneck and improving migration performance. Other options do not resolve the CPU constraint on the replication instance.

Answer

Enable Multi-AZ on the replication instance to improve availability and performance.

Answer

Change the target endpoint to use a larger instance class for the Aurora cluster.

Answer

Reduce the number of tables in the migration task to lower the load on the replication instance.

Question 20

A database specialist is monitoring an Amazon RDS for SQL Server DB instance. The specialist needs to identify the amount of free storage space available on the DB instance to prevent storage full issues. Which CloudWatch metric should be used?

Accepted Answer

FreeStorageSpace. FreeStorageSpace is the CloudWatch metric that reports the amount of available storage space in bytes for an Amazon RDS DB instance. Monitoring this metric allows the database specialist to set alarms and proactively increase storage or clean up data before the instance runs out of space, which can cause outages. It is a fundamental metric for storage management across all RDS engines.

Answer

DiskQueueDepth

Answer

FreeableMemory

Answer

ReadIOPS