DBS-C01 Monitoring and Troubleshooting Practice Test 13 — 15 Questions

Question 1

Which TWO CloudWatch metrics should be monitored to detect storage performance issues for an Amazon RDS for MySQL instance? (Choose two.)

Accepted Answer

WriteIOPS. Options C and E are correct. ReadIOPS and WriteIOPS measure the input/output operations per second, which directly indicate storage performance for an RDS MySQL instance. High or erratic IOPS can signal storage contention or saturation. Option A (NetworkReceiveThroughput) tracks network traffic, not storage. Option B (DatabaseConnections) reflects concurrent connections, unrelated to storage performance. Option D (CPUUtilization) measures CPU usage, which may impact overall performance but is not a direct storage metric.

Answer

NetworkReceiveThroughput

Answer

DatabaseConnections

Answer

CPUUtilization

Question 2

Which TWO actions should be taken to troubleshoot high memory usage on an Amazon ElastiCache for Redis node? (Choose two.)

Accepted Answer

Monitor the Evictions CloudWatch metric.. Monitoring the Evictions CloudWatch metric is the only valid action among the options for troubleshooting high memory usage on an Amazon ElastiCache for Redis node. Option B is incorrect because the maxmemory parameter is determined by the node type and cannot be increased; it is fixed. Options C, D, and E are not direct troubleshooting steps for memory pressure. Option C monitors CPU, not memory. Option D (enabling cluster mode) is a scaling action, not a troubleshooting step for an existing node. Option E (Reserved Memory) is a preventive setting but not a primary troubleshooting action.

Answer

Increase the maxmemory parameter to allow more memory usage.

Answer

Monitor CPUUtilization CloudWatch metric.

Answer

Enable cluster mode to distribute memory across shards.

Answer

Enable Reserved Memory parameter group setting.

Question 3

A company is using Amazon RDS for MySQL with Multi-AZ deployment. The database experiences a sudden increase in latency and the application reports timeouts. CloudWatch shows elevated 'ReadLatency' and 'WriteLatency' metrics, while 'CPUUtilization' and 'DatabaseConnections' remain normal. Which is the MOST likely cause?

Accepted Answer

A large transaction is being processed. A large transaction can cause increased latency without high CPU or connection count, as it may be waiting on disk I/O or replication. Option A is wrong because a runaway query consuming CPU would show elevated CPUUtilization, which is normal. Option B is wrong because a Multi-AZ failover would cause a brief spike in latency followed by recovery, not sustained latency. Option D is wrong because insufficient provisioned IOPS would typically show BurstBalance or IOPS metrics, not just ReadLatency and WriteLatency.

Answer

A runaway query is consuming CPU resources

Answer

A Multi-AZ failover occurred

Answer

The database has insufficient provisioned IOPS

Question 4

A developer reports that an Amazon RDS for PostgreSQL database instance's storage is full and the instance is in 'storage-full' state. The team wants to resolve this without downtime. Which action should be taken?

Accepted Answer

Modify the DB instance to increase allocated storage. Modifying the allocated storage for an RDS instance is a dynamic operation that can increase storage without downtime. Option A is wrong because creating a read replica requires the source to have available storage and does not resolve the storage issue on the primary instance. Option C is wrong because deleting old automated snapshots does not free up storage on the instance; snapshots are stored separately. Option D is wrong because rebooting does not free storage; it only restarts the instance.

Answer

Create a read replica and promote it

Answer

Delete old automated snapshots

Answer

Reboot the DB instance

Question 5

A company uses Amazon DynamoDB Global Tables with strong consistent reads. They notice that a write to us-east-1 is not visible in eu-west-1 after several seconds. Which configuration setting is MOST likely causing this behavior?

Accepted Answer

DynamoDB Streams is not enabled on the table. DynamoDB Global Tables require DynamoDB Streams to be enabled on the table. If streams are disabled, write operations in one region will not be replicated to other regions, causing the writes to never become visible. This matches the symptom of writes not appearing after several seconds. Option B (Auto Scaling) does not affect replication. Option C (LWW conflict resolution) is enabled by default and does not cause delays. Option D (strongly consistent reads) are not supported on Global Tables and would generate an error, not a delay.

Answer

Auto Scaling is configured for write capacity

Answer

Last writer wins (LWW) conflict resolution is disabled

Answer

Strongly consistent reads are used on a global table

Question 6

A database administrator notices that an Amazon RDS for Oracle DB instance's CPU utilization is consistently above 90% during peak hours. The application is read-heavy. Which action can reduce CPU load?

Accepted Answer

Create a read replica and direct read traffic to it. Creating a read replica offloads read traffic from the primary instance, reducing CPU utilization. For a read-heavy workload, this is an effective scaling strategy. Option A is incorrect because disabling Multi-AZ does not free up significant resources and reduces availability. Option B (increase storage) does not directly reduce CPU load; it addresses storage capacity. Option C (Performance Insights) helps identify performance bottlenecks but does not reduce CPU load by itself.

Answer

Disable Multi-AZ to free up resources

Answer

Increase the allocated storage

Answer

Enable Performance Insights to optimize queries

Question 7

A company uses Amazon Redshift for data warehousing. They run a daily ETL job that loads data into the cluster. Recently, the job started failing with 'Disk Full' errors. The cluster has 5 RA3 nodes. Which step should be taken to resolve the issue?

Accepted Answer

Resize the cluster to a larger node type or add more nodes. Resize the cluster to a larger node type or add more nodes. RA3 nodes use managed storage with a local cache, and a 'Disk Full' error typically indicates that the local cache or the overall storage limit for the cluster is exhausted. Resizing adds more local cache and increases the total managed storage capacity, resolving the disk full error. Option A is incorrect because disabling concurrency scaling does not free up disk space; it only affects query concurrency. Option B is incorrect because VACUUM reclaims space from deleted rows, but it requires temporary disk space; if the disk is already full, VACUUM may fail or not help. Option D is incorrect because Redshift Spectrum allows querying data directly from S3 without loading it into Redshift, but it does not resolve a disk full error on the Redshift cluster itself.

Answer

Disable concurrency scaling to free up resources

Answer

Run a VACUUM command to reclaim space from deleted rows

Answer

Enable Redshift Spectrum to offload queries to S3

Question 8

An application uses Amazon ElastiCache for Redis as a session store. Users report that sessions are being lost intermittently. The ElastiCache cluster has replication enabled with one replica. CloudWatch metrics show 'Evictions' spiking during peak hours. What is the MOST likely cause?

Accepted Answer

The cache's memory is full and the eviction policy is removing keys. A spike in 'Evictions' CloudWatch metric indicates that the cache's memory is full, and ElastiCache is evicting keys based on the configured eviction policy (e.g., allkeys-lru). This removal of keys directly causes session data to be lost. Option A is incorrect: replication lag can cause stale reads but not evictions or loss of keys. Option B is incorrect: encryption in transit does not affect memory usage or evictions. Option D is incorrect: automatic snapshots may cause a brief latency spike but do not result in evictions.

Answer

Replication lag between primary and replica is causing read failures

Answer

Encryption in transit is enabled and causes decryption errors

Answer

The cluster is performing automatic snapshots that block writes

Question 9

A company uses Amazon DynamoDB and notices that some queries are taking longer than expected. The table has a partition key only. The 'ConsumedReadCapacityUnits' is below the provisioned throughput. What is the most likely cause of the slow queries?

Accepted Answer

The partition key is not distributed evenly, causing hot partitions. If the partition key is not chosen well, data can be skewed, causing hot partitions. Even if total consumed capacity is below provisioned, a single partition may receive more requests than its share of capacity, causing throttling on that partition, which slows queries. Option A is wrong because DAX is a caching layer that speeds up reads, not slows them. Option B is wrong because global tables replication does not affect read latency on the source table. Option C is wrong because DynamoDB Streams do not consume read capacity for reads from the table; they use separate capacity.

Answer

DAX is misconfigured and slowing down reads

Answer

Global tables replication is causing delays

Answer

DynamoDB Streams is enabled and consuming read capacity

Question 10

A database administrator is troubleshooting an Amazon RDS for SQL Server instance that is experiencing high 'ReadIOPS' and 'ReadLatency'. The instance uses General Purpose SSD (gp2) storage. The 'BurstBalance' metric is 0%. What should the administrator do to improve performance?

Accepted Answer

Increase the allocated storage or switch to Provisioned IOPS. When BurstBalance is 0%, the gp2 volume has exhausted its burst credits and is operating at baseline IOPS. To improve performance, you can increase the volume size (which increases baseline IOPS) or switch to Provisioned IOPS (io1/io2) for consistent performance. Option A is wrong because enabling Multi-AZ does not increase I/O performance; it provides high availability. Option C is wrong because creating a read replica offloads read traffic but does not improve write performance or reduce latency on the primary instance. Option D is wrong because disabling automatic backups reduces storage I/O but does not directly improve ReadIOPS or ReadLatency; the primary issue is exhausted burst credits.

Answer

Enable Multi-AZ to distribute the load

Answer

Create a read replica to offload read traffic

Answer

Disable automatic backups to reduce I/O

Question 11

A company runs a critical application on Amazon RDS for PostgreSQL. The application team reports that the database occasionally becomes unresponsive for a few seconds. CloudWatch metrics show 'CPUSurplusCreditsCharged' and 'CPUSurplusCredits' are not 0. The instance is a db.t3.medium. What is the likely cause and how should it be fixed?

Accepted Answer

The instance is out of CPU credits and is being throttled; switch to a larger or non-burstable instance. T3 instances are burstable and use CPU credits. When credits are exhausted, they can use surplus credits, which incur charges. If the workload is consistently high, the instance may run out of credits and become throttled, causing unresponsiveness. The fix is to switch to T3 unlimited mode (but that incurs charges) or use a non-burstable instance (e.g., M5). Option B is wrong because Enhanced Monitoring provides detailed OS-level metrics but does not prevent CPU credit exhaustion. Option C is wrong because increasing allocated storage does not affect CPU credits; it improves I/O performance. Option D is wrong because enabling Multi-AZ provides high availability and failover but does not resolve CPU credit issues.

Answer

Enable Enhanced Monitoring to diagnose the issue

Answer

Increase the allocated storage to improve I/O

Answer

The instance is experiencing a failover; enable Multi-AZ

Question 12

A company is troubleshooting an Amazon DynamoDB table that is throttling write requests. The table has a partition key ('userId') and a sort key ('timestamp'). The 'WriteCapacityUnits' is set to 1000. CloudWatch shows 'ThrottledWriteRequests' but the 'ConsumedWriteCapacityUnits' is only 500. Which TWO actions could resolve the throttling?

Accepted Answer

Add a random suffix to the partition key to distribute writes more evenly. The issue is throttling on write requests despite consumed capacity below provisioned. This indicates a hot partition where one partition receives more writes than its limit (1000 WCU per partition). Option A (add random suffix to partition key) distributes writes across partitions, preventing any single partition from exceeding its limit. Option C (increase write capacity units) can increase the number of partitions, thereby distributing the load and potentially raising the per-partition limit. Option B is incorrect because DAX is a read cache and does not affect write throughput. Option D (Global Tables) does not resolve throttling and may add latency. Option E (removing sort key) does not address partition hotness.

Answer

Enable DynamoDB Accelerator (DAX) to cache writes

Answer

Enable Global Tables to replicate writes across regions

Answer

Remove the sort key and use only a partition key

Question 13

A database administrator is monitoring an Amazon RDS for MySQL instance and sees the following CloudWatch metrics: 'DiskQueueDepth' is consistently at 10, 'WriteLatency' is 20 ms, 'FreeStorageSpace' is less than 10% of total. The instance uses gp2 storage. Which THREE actions should be taken to improve performance?

Accepted Answer

Switch to Provisioned IOPS (io1 or io2) for consistent performance. High 'WriteLatency' and 'DiskQueueDepth' indicate an I/O bottleneck. Switching to Provisioned IOPS (io1 or io2) provides consistent low-latency I/O performance. Option B is correct: gp2 storage baseline IOPS scales with storage size. Increasing allocated storage raises the baseline IOPS, which can improve performance. Option C is correct: Low free storage space on gp2 can cause performance degradation because write operations may be throttled. Deleting unnecessary data frees up space and alleviates this issue. Option D is incorrect: Multi-AZ provides high availability and disaster recovery, not increased I/O capacity. It can add write latency due to synchronous replication. Option E is incorrect: Performance Insights is a monitoring tool for analyzing database performance; it helps identify slow queries but does not directly improve performance. Therefore, the correct actions are A, B, and C.

Answer

Enable Multi-AZ to increase I/O capacity

Answer

Enable Performance Insights to identify slow queries

Question 14

A company uses Amazon Redshift and notices that queries are taking longer than usual. CloudWatch metrics show 'CPUUtilization' is high and 'DiskSpace' is low. Which TWO actions can help improve query performance?

Accepted Answer

Add more nodes to the cluster. Adding nodes increases both compute capacity and storage, addressing high CPU and low disk space. Option E is correct because optimizing sort keys reduces the amount of data scanned per query, which lowers CPU usage and speeds up queries. Option A is incorrect because disabling concurrency scaling would reduce the cluster's ability to handle concurrent queries, increasing wait times. Option C is incorrect because Multi-AZ is not a feature of Amazon Redshift; it's used for RDS. Option D is incorrect because VACUUM reorganizes data but requires free disk space to operate; with low disk space, it may fail or not help.

Answer

Disable concurrency scaling to free resources

Answer

Enable Multi-AZ to distribute load

Answer

Run VACUUM to reclaim space

Question 15

A DevOps engineer notices that an Amazon RDS for PostgreSQL instance has been in 'storage-full' state for the past 30 minutes. The instance has 500 GB of General Purpose SSD (gp2) storage, and the free storage space is 0 bytes. The database is critical and cannot tolerate downtime. What is the MOST efficient way to resolve this issue while minimizing downtime?

Accepted Answer

Modify the DB instance to increase allocated storage to 1,000 GB. Modifying the storage allocation for an RDS instance can be done without downtime; the instance remains available during the modification. Increasing storage from 500 GB to 1,000 GB immediately resolves the 'storage-full' state. Option A is wrong because taking a snapshot and restoring to a new instance incurs downtime. Option C is wrong because enabling storage auto-scaling does not address the current full state; it only prevents future issues. Option D is wrong because deleting data may not free enough space and requires time-consuming intervention, risking downtime.

Answer

Take a snapshot of the DB instance and restore it to a new instance with larger storage

Answer

Enable storage auto-scaling on the DB instance

Answer

Delete unnecessary data, such as old logs or temporary tables