DBS-C01 Practice Exam 69 — 20 Questions

Question 1

A company uses Amazon RDS for MySQL with Multi-AZ deployment. The database experiences intermittent write latency spikes. CloudWatch shows elevated 'WriteLatency' and 'WriteIOPS' but normal 'CPUUtilization'. Which is the MOST likely cause?

Accepted Answer

The instance is exceeding the provisioned IOPS burst balance. Option D is correct because write spikes with high IOPS but low CPU often indicate storage performance issues like exceeding EBS burst balance. Option A is wrong because Multi-AZ replication does not cause write latency. Option B is wrong because read replica lag affects read, not write. Option C is wrong because parameter group changes require reboot and affect all operations, not intermittent.

Answer

A parameter group change was applied without rebooting

Answer

A read replica is being used for write operations

Answer

Multi-AZ replication is causing synchronous writes to the standby

Question 2

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. Option C is correct because 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. Option A is wrong because global tables do not cause slow queries on the source table. Option B is wrong because DynamoDB Streams do not affect read latency. Option D is wrong because DAX is a caching layer that speeds up reads, not slows them.

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 3

A company is running an Amazon DynamoDB table with on-demand capacity. The application is experiencing high latency for GetItem operations. CloudWatch shows that 'ThrottledRequests' is zero, but 'ConsumedReadCapacityUnits' is consistently below the provisioned limit. The table has a global secondary index (GSI) with a different partition key. What is the most likely cause of the high latency?

Accepted Answer

Throttling on the global secondary index due to uneven access patterns. Option D is correct because GSIs have their own capacity and if the GSI is throttled, writes to the base table can be throttled, affecting read latency. Option A is wrong because throttled requests are zero. Option B is wrong because on-demand capacity does not have a provisioned limit. Option C is wrong because hot partitions would cause throttling.

Answer

High write activity on the base table causing read latency

Answer

Insufficient provisioned read capacity on the base table

Answer

Throttling on the base table due to hot partitions

Question 4

A company uses Amazon DynamoDB with auto scaling enabled. The application experiences increased latency during peak hours. The DynamoDB table has a read capacity of 10,000 RCU and write capacity of 5,000 WCU. The auto scaling target utilization is 70%. During peak hours, the consumed read capacity reaches 8,000 RCU, but auto scaling does not increase capacity. What is the most likely reason?

Accepted Answer

The auto scaling configuration has a maximum capacity that prevents scaling beyond a certain limit.. Auto scaling uses the consumed capacity metric over a period. If the consumed capacity is consistently at 8,000 RCU, the target utilization is 70% of provisioned (10,000 RCU), so the current utilization is 80%, which is above the target. Auto scaling should increase capacity. However, auto scaling has a cooldown period and also scales based on sustained consumption. Option A is not correct because auto scaling can scale out. Option B is not correct because the table is not throttled yet. Option C is correct because auto scaling might be configured with a maximum capacity that limits scaling. Option D is not correct because auto scaling can increase RCU if needed.

Answer

The consumed capacity is still below the provisioned capacity, so no throttling occurs, and auto scaling does not trigger.

Answer

Auto scaling for DynamoDB does not support increasing read capacity; it only decreases capacity.

Answer

Auto scaling only scales out when the consumed capacity exceeds the provisioned capacity.

Question 5

A company is using Amazon RDS for MySQL with Multi-AZ deployment. The application team reports increased latency during peak hours. Which AWS service should the database specialist use to identify the root cause?

Accepted Answer

Enable Performance Insights for the RDS instance and analyze the database load.. Option B is correct because Performance Insights provides database performance metrics and helps identify bottlenecks. Option A is wrong because CloudWatch Metrics Dashboard shows aggregated metrics but does not provide detailed database performance analysis. Option C is wrong because AWS Config is for resource configuration auditing. Option D is wrong because Amazon Inspector is for security assessments.

Answer

Enable AWS Config to track configuration changes to the RDS instance.

Answer

Use the CloudWatch Metrics Dashboard to analyze database connections.

Answer

Run an Amazon Inspector assessment on the RDS instance.

Question 6

A company is using Amazon DynamoDB with provisioned capacity. The application is experiencing throttling on write requests. The database specialist needs to identify the cause. Which THREE metrics should be reviewed in CloudWatch? (Select THREE.)

Accepted Answer

ConsumedWriteCapacityUnits. Option A is correct because 'ThrottledWriteRequests' directly indicates throttling. Option B is correct because 'WriteThrottleEvents' is another metric for throttling events. Option C is correct because 'ConsumedWriteCapacityUnits' helps understand if provisioned capacity is being fully used. Option D is wrong because 'ReadThrottleEvents' is for reads, not writes. Option E is wrong because 'SuccessfulRequestLatency' measures latency, not throttling.

Answer

ReadThrottleEvents

Answer

SuccessfulRequestLatency

Question 7

A database administrator is troubleshooting an issue where an Amazon RDS for PostgreSQL DB instance is not allowing connections. The administrator checks the security group and network ACLs, and they are correctly configured. What is the next step to diagnose the issue?

Accepted Answer

Review the DB instance error logs in Amazon CloudWatch. Option A is correct because checking DB instance logs can reveal connection issues like authentication failures or max connections reached. Option B is wrong because rebooting may not resolve the underlying issue. Option C is wrong because modifying the parameter group is not diagnostic. Option D is wrong because creating a snapshot is not a diagnostic step.

Answer

Reboot the DB instance

Answer

Modify the DB instance's parameter group

Answer

Create a DB snapshot

Question 8

A company is running an Amazon Aurora MySQL-Compatible DB cluster. The application is experiencing increased latency during peak hours. The DB cluster's CPU utilization is at 40%, but the ReadReplicaLag metric is high. Which of the following is the most likely cause?

Accepted Answer

The writer instance is experiencing I/O bottlenecks, causing slow replication. Option A is correct because high replica lag indicates the replica is falling behind, often due to insufficient I/O capacity on the writer or replica. Option B is wrong because read replicas handle SELECT queries. Option C is wrong because binary log retention does not affect replica lag directly. Option D is wrong because the DB cluster parameter group is shared.

Answer

The read replica is receiving too many write requests

Answer

The DB cluster parameter group is misconfigured

Answer

The binary log retention period is too long

Question 9

A DevOps engineer notices that an Amazon DynamoDB table's read capacity is frequently throttled during peak hours. The table has read-once, read-many workload. Which action is MOST cost-effective to reduce throttling?

Accepted Answer

Enable DynamoDB Accelerator (DAX). Option B is correct because DynamoDB Accelerator (DAX) caches reads, reducing read capacity consumption. Option A is wrong because increasing read capacity costs more. Option C is wrong because auto-scaling still incurs cost. Option D is wrong because changing to On-Demand may be more expensive for predictable workloads.

Answer

Enable auto-scaling for read capacity

Answer

Switch to On-Demand capacity mode

Answer

Increase the provisioned read capacity units

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. Option D is correct because 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). Option A is wrong because enabling Multi-AZ does not increase I/O performance. Option B is wrong because disabling backups reduces CPU but not IOPS. Option C is wrong because creating a read replica does not improve write performance.

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's Amazon RDS for MySQL DB instance is experiencing high CPU utilization. The DB instance is a db.r5.large with 200 GB of General Purpose SSD (gp2) storage. The application is performing many complex queries. Which action would BEST reduce CPU utilization without changing the application code?

Accepted Answer

Scale up the DB instance to db.r5.xlarge. Option A is correct because scaling up the instance provides more CPU capacity. Option B is wrong because read replicas help with read scaling but not CPU on the writer. Option C is wrong because gp3 storage does not affect CPU. Option D is wrong because changing the query cache is unlikely to significantly reduce CPU.

Answer

Create a read replica and route write queries to it

Answer

Modify the storage type to gp3

Answer

Enable the query cache parameter

Question 12

A database administrator is troubleshooting a failover event for an Amazon RDS for SQL Server Multi-AZ DB instance. The failover occurred automatically. Which AWS service or feature should the administrator use to view the failover history and the reason for the failover?

Accepted Answer

The Amazon RDS console Events page.. Amazon RDS events are stored in the RDS console under 'Events' and also in CloudTrail. But the best place to see failover reasons is the RDS console events. Option B is correct because the RDS console shows events like 'failover' with reasons. Option A is wrong because CloudTrail records API calls, not internal failover reasons. Option C is wrong because CloudWatch Logs does not automatically log failover reasons. Option D is wrong because StatusInsis not a service.

Answer

Amazon CloudWatch Logs for the DB instance.

Answer

AWS CloudTrail logs to view the failover API call.

Answer

The AWS Status Dashboard.

Question 13

A database specialist is troubleshooting an Amazon RDS for PostgreSQL instance that is experiencing intermittent connection timeouts. The application logs show errors like 'FATAL: remaining connection slots are reserved for non-replication superuser connections'. The max_connections parameter is set to 100. What should the specialist do to resolve this issue?

Accepted Answer

Modify the 'max_connections' parameter to a higher value and reboot the instance.. Option C is correct because the error indicates connection pool exhaustion. Increasing max_connections allows more concurrent connections. Option A is wrong because the error is about connection slots, not idle sessions. Option B is wrong because reserving more slots for superusers does not address the root cause. Option D is wrong because the error is not due to replication slots.

Answer

Increase the 'max_replication_slots' parameter to allow more replication connections.

Answer

Increase the value of the 'superuser_reserved_connections' parameter.

Answer

Enable RDS Proxy to manage database connections efficiently.

Question 14

A database specialist is troubleshooting an Amazon RDS for PostgreSQL instance that has high replication lag between the primary and a read replica. Which TWO metrics should the specialist review to identify the cause? (Select TWO.)

Accepted Answer

ReadIOPS on the replica. Option A is correct because 'ReplicaLag' directly measures the lag. Option B is correct because 'ReadIOPS' can indicate heavy read activity on the replica that may cause lag. Option C is wrong because 'WriteIOPS' on the primary does not directly indicate replica lag. Option D is wrong because 'DatabaseConnections' is about connections, not replication. Option E is wrong because 'NetworkThroughput' is not a direct indicator of replication lag.

Answer

WriteIOPS on the primary

Answer

DatabaseConnections on the primary

Answer

NetworkThroughput between primary and replica

Question 15

A company is using Amazon DynamoDB and wants to monitor the read/write capacity utilization of a table. Which TWO AWS services can be used to set up alarms for capacity consumption?

Accepted Answer

Amazon CloudWatch Logs. Options A and B are correct. CloudWatch provides metrics like ConsumedReadCapacityUnits and can trigger alarms. CloudWatch Logs can capture log events but is not directly used for capacity alarms. CloudTrail records API calls, not capacity metrics. DynamoDB Auto Scaling adjusts capacity but does not monitor. AWS Config tracks configuration changes, not capacity.

Answer

Amazon DynamoDB Auto Scaling

Answer

AWS CloudTrail

Answer

AWS Config

Question 16

A company is using Amazon DynamoDB Accelerator (DAX) to improve read performance. Recently, the cache hit ratio has dropped significantly. The application uses strongly consistent reads. What is the most likely cause of the low cache hit ratio?

Accepted Answer

The application is using strongly consistent reads, which bypass the DAX cache. Option C is correct because DAX caches eventually consistent reads, not strongly consistent reads. Option A is wrong because TTL affects item expiration but not the consistency model. Option B is wrong because write capacity does not directly affect cache hits. Option D is wrong because the DAX cluster size affects performance but not the consistency mismatch.

Answer

The DynamoDB table's write capacity is too low

Answer

The DAX cluster has too few nodes

Answer

The DAX cluster's TTL is set too low

Question 17

A database specialist is troubleshooting an Amazon Aurora MySQL cluster. The writer instance's CPU is at 90% and there are frequent 'Lock wait timeout exceeded' errors. The application uses many short-lived connections. What should the specialist do FIRST to reduce lock contention?

Accepted Answer

Enable RDS Proxy to pool database connections. Option A is correct because enabling RDS Proxy reduces connection churn and pools connections, reducing lock contention. Option B is wrong because increasing instance size adds CPU but doesn't directly address lock contention. Option C is wrong because reducing connections may increase contention per connection. Option D is wrong because read replicas don't handle write locks.

Answer

Add additional read replicas to distribute read traffic

Answer

Increase the instance size to handle more concurrent transactions

Answer

Reduce the maximum number of connections in the application

Question 18

A company is using Amazon RDS for MySQL and needs to monitor for slow queries. Which TWO AWS services can be used to capture and analyze slow query logs? (Choose TWO.)

Accepted Answer

Amazon RDS Performance Insights. Options A and C are correct because CloudWatch Logs can be used to stream RDS logs, and Performance Insights can help identify slow queries. Option B is wrong because CloudTrail records API calls, not database logs. Option D is wrong because S3 is a storage service, not a monitoring service. Option E is wrong because Config records configuration changes.

Answer

Amazon S3

Answer

AWS Config

Answer

AWS CloudTrail

Question 19

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. Option A is correct because a hot partition can throttle even if overall capacity is underutilized; adjusting the partition key design can distribute writes. Option D is correct because using DynamoDB Accelerator (DAX) can offload read traffic but does not affect writes; actually DAX is for reads. Option B is correct because increasing write capacity ensures enough capacity for peaks. Option C is wrong because removing the sort key changes the table structure and may not help with partition hotness. Option E is wrong because Global Tables replicate writes and may increase throttling. So correct answers: B and E? Let's re-evaluate: The issue is write throttling despite consumed capacity below provisioned. This indicates a hot partition. Option A: Adding a random suffix to partition key helps distribute writes across partitions. Option B: Increasing write capacity may help if the hot partition is still within limits, but if a single partition is throttled due to its own limit, increasing total capacity may increase the partition limit. Actually, DynamoDB's partition capacity is 1000 WCU per partition; if a single partition receives more than 1000 WCU, it throttles. Increasing total WCU may increase the partition count, distributing the load. Option C: Removing the sort key does not affect partition distribution. Option D: DAX is a read cache, not for writes. Option E: Global Tables add more write replication and could increase throttling. So likely correct: A and B. Option A is a design change to avoid hot partition. Option B increases total capacity, which may increase partitions. So answer: A, B.

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 20

A company is running an Amazon DynamoDB table with provisioned capacity. The table has a partition key of 'user_id' and a sort key of 'timestamp'. The application performs frequent Query operations using the partition key and a range of sort keys. Recently, the 'ThrottledRequests' metric has spiked. The read and write capacity units are consistently at 80% utilization. What is the most effective way to resolve the throttling?

Accepted Answer

Enable DynamoDB Auto Scaling with a higher target utilization. Option D is correct because using an adaptive capacity add-on allows DynamoDB to automatically manage throughput for hot partitions. Option A is wrong because increasing capacity units may not help if throttling is due to hot partitions. Option B is wrong because GSI does not directly solve hot partition throttling. Option C is wrong because changing partition key distribution would require table redesign and data migration.

Answer

Increase the provisioned read and write capacity units

Answer

Add a global secondary index with a different partition key

Answer

Change the partition key to a more uniformly distributed attribute