DBS-C01 Management and Operations Practice Test 7 — 15 Questions

Question 1

A company is running a production Amazon RDS for MySQL Multi-AZ DB instance. The database administrator needs to perform a minor version upgrade with minimal downtime. Which TWO actions should be taken? (Choose TWO.)

Accepted Answer

Modify the DB instance to enable automatic minor version upgrade.. Enabling automatic minor version upgrade allows the upgrade to occur during the maintenance window with minimal downtime. Applying the upgrade immediately during the maintenance window also minimizes impact. Stopping the instance causes downtime. Modifying the DB instance to single-AZ increases downtime risk. Creating a read replica does not help upgrade the primary.

Answer

Create a read replica, upgrade the replica, and promote it.

Answer

Modify the DB instance to be a Single-AZ deployment to simplify the upgrade.

Answer

Stop the DB instance before applying the upgrade.

Question 2

A company is using Amazon DynamoDB with provisioned capacity for a table that experiences unpredictable traffic spikes. The table's read capacity is often underutilized, but occasionally throttling occurs. Which THREE steps should be taken to improve performance and cost? (Choose THREE.)

Accepted Answer

Switch the table to on-demand capacity mode.. Switching to on-demand capacity handles unpredictable spikes automatically and reduces throttling. Using DynamoDB Accelerator (DAX) reduces read load by caching. Auto scaling adjusts capacity based on load, but on-demand is better for unpredictable spikes. Reducing read capacity units would worsen throttling. Disabling auto scaling is counterproductive.

Answer

Reduce the provisioned read capacity units to save cost.

Answer

Disable auto scaling to avoid cost fluctuations.

Question 3

A company is using Amazon RDS for MariaDB. The database administrator wants to monitor the database for slow queries. Which TWO services can be used to achieve this? (Choose TWO.)

Accepted Answer

Amazon RDS Performance Insights. RDS Performance Insights provides a dashboard for database performance and can identify slow queries. RDS Enhanced Monitoring provides OS-level metrics but not query-specific. CloudWatch Logs can capture slow query logs if enabled. CloudTrail logs API calls. AWS Config tracks configuration.

Answer

AWS Config

Answer

Amazon RDS Enhanced Monitoring

Answer

AWS CloudTrail

Question 4

A company is running a production Amazon RDS for MySQL DB instance. The database size is 500 GB and the workload is write-heavy. The team notices that the automated backups are taking longer than expected and are impacting the performance during the backup window. Which action should be taken to minimize the performance impact?

Accepted Answer

Create a read replica and configure automated backups on the replica.. Option D is correct because creating a read replica and taking backups from it offloads the backup load from the primary instance. Option A is wrong because disabling backups is risky for production. Option B is wrong because it affects the start time but not the performance impact. Option C is wrong because increasing instance size may reduce backup duration but does not directly minimize the performance impact; it also adds cost.

Answer

Disable automated backups and rely on manual snapshots taken during off-peak hours.

Answer

Increase the DB instance size to improve backup performance.

Answer

Move the backup window to a time when the workload is lowest.

Question 5

A company is using Amazon Aurora MySQL-Compatible Edition. The database has frequent deadlocks, and the application team suspects that the isolation level is causing the issue. The current isolation level is REPEATABLE READ. The team wants to reduce deadlocks while maintaining data consistency. Which isolation level should be recommended?

Accepted Answer

READ COMMITTED. Option A is correct because READ COMMITTED reduces locking and is less prone to deadlocks compared to REPEATABLE READ, while still providing consistent reads at the statement level. Option B is wrong because READ UNCOMMITTED can cause dirty reads and is not typically used for transactional databases. Option C is wrong because SERIALIZABLE increases locking and can increase deadlocks. Option D is wrong because SNAPSHOT ISOLATION is not directly supported by MySQL; it is a SQL Server feature.

Answer

READ UNCOMMITTED

Answer

SNAPSHOT ISOLATION

Answer

SERIALIZABLE

Question 6

A company has an Amazon DynamoDB table that stores session data for a web application. The table's read capacity units (RCUs) are consistently near 100% utilization during peak hours, causing throttling. The application can tolerate eventually consistent reads. Which action should the application team take to reduce throttling?

Accepted Answer

Change the read consistency to eventually consistent.. Option A is correct because using eventually consistent reads consumes only half the RCUs compared to strongly consistent reads, effectively doubling the read capacity. Option B is wrong because DynamoDB Accelerator (DAX) is an in-memory cache that can reduce read load but does not directly address the RCU consumption for reads that still hit the table. Option C is wrong because increasing RCUs would solve throttling but increase costs unnecessarily if eventually consistent reads suffice. Option D is wrong because decreasing RCUs would worsen throttling.

Answer

Decrease the provisioned RCUs for the table.

Answer

Enable DynamoDB Accelerator (DAX) to cache the session data.

Answer

Increase the provisioned RCUs for the table.

Question 7

A database administrator is troubleshooting a slow-running query on an Amazon RDS for PostgreSQL DB instance. The query plan shows a sequential scan on a large table. The table has a primary key and an index on the column used in the WHERE clause. Why might the query optimizer choose a sequential scan over an index scan?

Accepted Answer

The query is expected to return a large percentage of rows.. Option B is correct because if the optimizer estimates that a large percentage of rows will be returned, a sequential scan can be more efficient than random I/O from an index. Option A is wrong because outdated statistics can cause suboptimal plans, but the question asks for a reason the planner might choose sequential scan; outdated stats could lead to either choice. Option C is wrong because the presence of an index does not force its use; the optimizer decides. Option D is wrong because the query has a WHERE clause, so a full table scan is not the only option, but it may be chosen due to the selectivity.

Answer

The query is a SELECT * without a WHERE clause.

Answer

The table's statistics are outdated.

Answer

The index on the column is not being used because it is a composite index with a different column order.

Question 8

A company is migrating an on-premises Oracle database to Amazon Aurora PostgreSQL. The database has several stored procedures that use Oracle-specific PL/SQL. The team needs to minimize manual code changes. Which AWS service or tool should be used to automate the conversion of the stored procedures?

Accepted Answer

AWS Schema Conversion Tool (AWS SCT). Option B is correct because the AWS Schema Conversion Tool (AWS SCT) is designed to convert database schemas, including stored procedures, from one engine to another. Option A is wrong because DMS is for data migration, not schema or code conversion. Option C is wrong because SCT can handle the conversion, and a manual rewrite is not necessary; SCT automates most of it. Option D is wrong because the PostgreSQL compatibility mode in Amazon Aurora does not automatically convert Oracle PL/SQL.

Answer

Amazon Aurora PostgreSQL native compatibility

Answer

AWS Database Migration Service (AWS DMS)

Answer

Manual rewrite using PostgreSQL PL/pgSQL

Question 9

An application is experiencing increased latency when writing to an Amazon DynamoDB table. The table uses on-demand capacity mode. The CloudWatch metric 'WriteThrottleEvents' is zero. What is the most likely cause of the increased latency?

Accepted Answer

A hot partition is causing excessive write traffic to a single partition.. Option C is correct because on-demand tables can throttle if you exceed the previous peak traffic by more than double in a short time, but since WriteThrottleEvents is zero, latency is likely due to hot partitions. Option A is wrong because throttling would show WriteThrottleEvents > 0. Option B is wrong because insufficient WCUs is not applicable for on-demand. Option D is wrong because while DAX can reduce read latency, it does not affect write latency.

Answer

The write capacity units (WCUs) are set too low.

Answer

DynamoDB Accelerator (DAX) is not configured for writes.

Answer

The table is experiencing write throttling due to exceeding the provisioned write capacity.

Question 10

A company is running an Amazon RDS for SQL Server Multi-AZ DB instance. During a recent failover test, the application experienced a timeout of 60 seconds. The application uses a connection string that points to the CNAME of the DB instance. Which configuration change would reduce the failover time?

Accepted Answer

Enable TDS Keep-Alive on the client side to detect and recover from connection drops faster.. Option D is correct because enabling TDS Keep-Alive on the client side ensures the connection is monitored and can be re-established quickly after failover. Option A is wrong because the CNAME is the correct endpoint for Multi-AZ, and changing it would not help. Option B is wrong because read replicas are for read scaling, not failover. Option C is wrong because Multi-AZ already provides automatic failover; disabling it would increase downtime.

Answer

Create a read replica and promote it to a standalone instance during failover.

Answer

Modify the application to use the IP address of the DB instance instead of the CNAME.

Answer

Disable Multi-AZ and use a single-AZ instance to avoid failover overhead.

Question 11

A company is using Amazon ElastiCache for Redis as a caching layer for a high-traffic web application. The cache hit ratio has dropped from 95% to 70% after a recent deployment that changed the cache key structure. The application team wants to improve the hit ratio without increasing the cache memory. Which action should they take?

Accepted Answer

Implement a consistent hashing algorithm for key distribution.. Option B is correct because using a consistent hashing algorithm ensures that keys are evenly distributed across nodes, reducing evictions and improving hit ratio. Option A is wrong because increasing TTL may cause stale data but does not directly improve hit ratio. Option C is wrong because Cluster Mode Off would limit scalability but not necessarily improve hit ratio. Option D is wrong because random TTLs can lead to premature evictions and reduce hit ratio.

Answer

Disable Cluster Mode and use a single node.

Answer

Increase the TTL (time-to-live) for all cache keys.

Answer

Use random TTLs to spread out expiration times.

Question 12

A company has an Amazon DynamoDB table that stores IoT sensor data. The table has a partition key of device_id and a sort key of timestamp. The team wants to efficiently retrieve the latest reading for each device. Which query pattern should be used?

Accepted Answer

Query with ScanIndexForward=false and Limit=1. Option A is correct because using the Query API with ScanIndexForward set to false and Limit 1 will return the most recent item for a given partition key. Option B is wrong because ScanIndexForward=true returns items in ascending order, which would give the oldest item first. Option C is wrong because Scan operations scan the entire table and are inefficient. Option D is wrong because GetItem requires both partition and sort key; the sort key value is not known in advance.

Answer

Scan with FilterExpression to get the latest timestamp for each device

Answer

Query with ScanIndexForward=true and Limit=1

Answer

GetItem with the device_id and timestamp values

Question 13

A company is migrating a PostgreSQL database to Amazon Aurora PostgreSQL. The database has a large table that is frequently accessed. The team wants to minimize downtime during the migration. Which TWO strategies should be used together?

Accepted Answer

Use AWS DMS to create a target Aurora DB cluster and replicate data.. Options B and D are correct because using AWS DMS with ongoing replication allows for near-zero downtime migration, and creating an Aurora read replica from a PostgreSQL instance is not possible; instead, DMS is the correct tool. Option A is wrong because taking a snapshot and restoring requires downtime. Option C is wrong because AWS SCT is for schema conversion, not data migration. Option E is wrong because there is no direct replication from PostgreSQL to Aurora without DMS.

Answer

Take a manual snapshot of the source database and restore it to Aurora.

Answer

Use AWS Schema Conversion Tool (AWS SCT) to convert the schema.

Answer

Configure Aurora as a read replica of the PostgreSQL instance.

Question 14

A company is running Amazon RDS for Oracle with a Multi-AZ deployment. The database is experiencing performance degradation due to high I/O waits. The team suspects that the issue is related to the transaction log (redo log) writes. Which THREE metrics should be monitored in Amazon CloudWatch to diagnose the issue?

Accepted Answer

DiskQueueDepth. Options A, C, and E are correct because high redo log sync time, high redo log file sync waits, and high disk queue depth are indicators of I/O bottlenecks affecting redo log writes. Option B is wrong because read latency is not directly related to redo log writes. Option D is wrong because CPU utilization may be high but does not directly indicate redo log issues.

Answer

CPUUtilization

Answer

ReadLatency

Question 15

A company is using Amazon DynamoDB with provisioned capacity. The table's read capacity is consistently underutilized, but the write capacity is frequently maxed out. The team wants to optimize costs while maintaining performance. Which TWO actions should be taken?

Accepted Answer

Use DynamoDB Auto Scaling for write capacity.. Options B and C are correct because using DynamoDB Auto Scaling for writes will adjust capacity based on demand, and reducing provisioned reads to actual usage will save costs. Option A is wrong because switching to on-demand may increase costs if the workload is predictable. Option D is wrong because reducing writes would cause throttling. Option E is wrong because using DAX does not reduce write costs.

Answer

Switch the table to on-demand capacity mode.

Answer

Enable DynamoDB Accelerator (DAX) to offload reads.

Answer

Increase the provisioned write capacity to handle spikes.