DBS-C01 Monitoring and Troubleshooting Practice Test 3 — 15 Questions

Question 1

Match each backup/restore concept to its AWS database feature.

Accepted Answer

Automated Backup: Automatically created daily backups of a DB instance with a retention period (RDS). Correct matches: Automated Backup corresponds to RDS automated backups (daily, retention period), Manual Snapshot corresponds to user-initiated RDS snapshots (stored in S3), and PITR corresponds to DynamoDB's ability to restore to any point in the last 35 days. Common confusions involve swapping the definitions of automated and manual backups.

Answer

Automated Backup: User-initiated backup of a DB instance stored in S3

Answer

Manual Snapshot: Automatically created daily backups with retention period

Question 2

A company is running an Amazon RDS for MySQL Multi-AZ DB instance. They notice that the application is experiencing increased latency during peak hours. The DB instance's CPU utilization is consistently above 80%, and the Read Latency metric is high. Which action would most effectively reduce the latency without requiring application changes?

Accepted Answer

Create a read replica and direct read queries to it.. Creating a read replica offloads read queries from the primary DB instance, reducing read latency and CPU utilization without requiring application changes. Option B is incorrect because disabling Multi-AZ removes the standby instance, reducing availability and not addressing read latency. Option C is incorrect because increasing the instance class may improve performance but does not specifically offload read traffic; read replicas are more targeted for read-heavy workloads. Option D is incorrect because the instance already has Multi-AZ enabled; enabling it again has no effect and does not reduce read latency.

Answer

Disable Multi-AZ to free up resources.

Answer

Increase the DB instance class to a larger size.

Answer

Enable Multi-AZ on the DB instance.

Question 3

A team is using Amazon DynamoDB with auto scaling enabled. They notice that some requests are returning ProvisionedThroughputExceededException errors during a sudden traffic spike. The application uses strong consistent reads. Which two actions would help mitigate the throttling without over-provisioning capacity? (Choose two.)

Accepted Answer

Implement DynamoDB Accelerator (DAX) to cache read results.. DAX acts as an in-memory cache for DynamoDB, reducing the number of read requests that consume provisioned throughput, thus mitigating throttling without increasing capacity. Option B is correct because adaptive capacity enables DynamoDB to automatically use unused throughput from other partitions to absorb traffic spikes, reducing ProvisionedThroughputExceededException errors. Option C is wrong because while eventually consistent reads consume half the read capacity, the application uses strong consistent reads, which may be required for data consistency, and this switch may not be acceptable. Option D is wrong because disabling auto scaling and manually setting higher capacity would lead to over-provisioning and increased cost, contrary to the goal of mitigating throttling without over-provisioning. Option E is wrong because burst capacity is limited and not guaranteed; it can handle short spikes but is not a reliable mitigation for sudden spikes.

Answer

Switch to eventually consistent reads for all queries.

Answer

Disable auto scaling and manually set higher capacity.

Answer

Use DynamoDB burst capacity for the spike.

Question 4

A developer is troubleshooting a slow-running query on an Amazon RDS for PostgreSQL instance. The query is performing a sequential scan on a large table. Which AWS service or feature should the developer use to identify the missing index?

Accepted Answer

Amazon RDS Performance Insights. Amazon RDS Performance Insights provides database performance analysis with a dashboard that helps identify performance bottlenecks, such as missing indexes causing sequential scans. Option A is wrong because Amazon RDS Enhanced Monitoring provides OS-level metrics, not database query details. Option B is wrong because AWS CloudTrail logs API calls to AWS services, not database queries. Option D is wrong because Amazon CloudWatch Logs can store database logs but does not analyze query performance to identify missing indexes.

Answer

Amazon RDS Enhanced Monitoring

Answer

AWS CloudTrail

Answer

Amazon CloudWatch Logs

Question 5

A company uses Amazon ElastiCache for Redis as a caching layer for a web application. They observe a sudden increase in CPU utilization on the cache cluster, and the application experiences higher latency. Which action should be taken to diagnose the issue?

Accepted Answer

Monitor Amazon CloudWatch metrics for the ElastiCache cluster to identify the cause.. The first step in diagnosing a sudden CPU utilization increase and latency in ElastiCache is to monitor CloudWatch metrics such as CPUUtilization, CacheHits, CacheMisses, and EngineCPUUtilization to identify patterns or bottlenecks. Option A is incorrect because ElastiCache for Redis does not support query profiling; that feature is for RDS. Option C is incorrect because disabling persistence (e.g., AOF or RDB) reduces durability but is not a diagnostic action and may not address CPU issues. Option D is incorrect because scaling up should only be considered after analyzing metrics to determine if capacity is the actual problem.

Answer

Enable query profiling on the ElastiCache cluster.

Answer

Disable persistence to reduce CPU overhead.

Answer

Immediately scale up to a larger node type.

Question 6

A company runs an Amazon Aurora MySQL database cluster with one writer and two readers. The application suddenly fails with 'Too many connections' error. The writer instance's maximum connections is set to 1000. Which configuration change would best resolve the issue while maintaining high availability?

Accepted Answer

Enable Amazon RDS Proxy for the database cluster.. Amazon RDS Proxy acts as a connection pooler that manages database connections efficiently. By reducing connection churn and reusing connections, it prevents the 'Too many connections' error without overloading the instance. Option B is incorrect because simply increasing max_connections could lead to resource exhaustion and degradation of performance. Option C is incorrect because read replicas cannot accept write traffic; they are read-only. Option D is incorrect because manually killing idle connections is a temporary fix and not a configuration change; it does not prevent the issue from recurring.

Answer

Increase the max_connections parameter on the writer instance to 5000.

Answer

Redirect all write requests to one of the read replicas.

Answer

Manually kill idle connections from the database.

Question 7

A developer is troubleshooting an application that is unable to write to a DynamoDB table. The above IAM policy is attached to the IAM role used by the application. What is the likely cause?

Accepted Answer

The Deny statement overrides the Allow statement, blocking all DynamoDB actions.. The Deny statement for all DynamoDB actions overrides the Allow for PutItem. Deny statements always take precedence over Allow statements. Option B is incorrect because the table name in the Resource ARN is correct. Option C is incorrect because the IAM user does exist. Option D is incorrect because the role is assumed correctly.

Answer

The table name in the Resource ARN is incorrect.

Answer

The IAM user does not exist.

Answer

The role is not correctly assumed by the application.

Question 8

A company uses Amazon DynamoDB with global tables. They notice that changes made in one region are not appearing in another region after several minutes. Which CloudWatch metric should be monitored to check the replication lag?

Accepted Answer

ReplicationLatency. ReplicationLatency measures the time between the last update on the source table and the last update on the replica table. Option A (ConsumedWriteCapacityUnits) is wrong because it measures write capacity usage, not replication lag. Option B (SuccessfulRequestLatency) is wrong because it measures request latency, not replication lag. Option D (ThrottledRequests) is wrong because it indicates throttling, not replication lag.

Answer

ConsumedWriteCapacityUnits

Answer

SuccessfulRequestLatency

Answer

ThrottledRequests

Question 9

A team is troubleshooting an Amazon RDS for SQL Server instance that is running out of storage. The instance uses General Purpose SSD (gp2) storage. The team wants to increase storage without downtime. Which action should they take?

Accepted Answer

Modify the DB instance to increase allocated storage.. Amazon RDS allows you to modify the allocated storage for a DB instance dynamically without downtime; the change takes effect during the next maintenance window or can be applied immediately. Option A is incorrect because migrating from gp2 to gp3 changes the storage type but does not increase the storage capacity. Option B is incorrect because adding a read replica does not increase storage on the primary instance; it only offloads read traffic. Option C is incorrect because while you can restore a snapshot to a larger instance, this process involves downtime and is not as straightforward as modifying the storage directly.

Answer

Migrate to gp3 storage.

Answer

Add a read replica to offload queries.

Answer

Take a snapshot and restore to a larger instance.

Question 10

A developer is using AWS Database Migration Service (DMS) to migrate a database from on-premises to Amazon RDS. The migration task is failing with 'Insufficient memory' error. Which resource should be increased to resolve this?

Accepted Answer

Increase the size of the DMS replication instance.. The DMS replication instance may have insufficient memory. Increasing its size provides more memory. Option B is wrong because source database memory is not controlled by DMS. Option C is wrong because S3 is not involved in the DMS process by default. Option D is wrong because target RDS instance memory may not be the bottleneck.

Answer

Increase the memory on the source database.

Answer

Increase the Amazon S3 bucket size for staging.

Answer

Increase the memory on the target RDS instance.

Question 11

A developer is trying to connect to an RDS for PostgreSQL instance using the endpoint shown in the exhibit. The connection fails with a timeout. Which of the following is the most likely cause?

Accepted Answer

The security group does not allow inbound traffic on port 5432 from the client IP.. The most likely cause is that the security group does not allow inbound traffic on port 5432 from the client IP, causing a timeout. Option A is incorrect because the endpoint is correctly provided by AWS; an incorrect endpoint would produce a different error. Option B is incorrect because SSL encryption is not required by default; if it were, the error would be an SSL handshake failure, not a timeout. Option D is incorrect because Multi-AZ configurations use the same endpoint; no separate endpoint is needed.

Answer

The endpoint address is incorrect.

Answer

The DB instance requires SSL encryption to connect.

Answer

The DB instance is in a Multi-AZ configuration and requires a different endpoint.

Question 12

A company uses Amazon DynamoDB with auto scaling enabled. They notice that a table's write capacity is frequently throttled during a specific hour each day. The access pattern is uniform across partitions. Which action would resolve the throttling without manual intervention?

Accepted Answer

Increase the minimum provisioned capacity in auto scaling.. When DynamoDB auto scaling is enabled, throttling can occur if the table's write capacity demand spikes faster than auto scaling can increase capacity. The 'minimum provisioned capacity' in the auto scaling policy sets a floor for the capacity units. By increasing this minimum, the table starts with a higher base capacity, reducing the likelihood of throttling during predictable peak hours. Option A is incorrect because DAX is a caching layer for reads, not writes. Option B is incorrect because disabling auto scaling requires manual intervention. Option C is incorrect because table partitioning in DynamoDB is managed automatically based on provisioned capacity; you cannot manually split partitions.

Answer

Enable DynamoDB Accelerator (DAX) to cache writes.

Answer

Disable auto scaling and set a fixed higher capacity.

Answer

Create a larger number of partitions by splitting the table.

Question 13

A company is monitoring an Amazon Aurora MySQL DB cluster. They observe that the AuroraReplicaLagMaximum metric is consistently above 10 seconds. Which action would best reduce the replica lag?

Accepted Answer

Increase the instance size of the reader.. Increasing the instance size of the reader can improve its ability to apply changes faster. Option A is wrong because increasing the writer size may not help if the reader is the bottleneck. Option C is wrong because reducing transaction size helps but may not be feasible. Option D is wrong because Multi-AZ is always enabled for Aurora.

Answer

Increase the instance size of the writer.

Answer

Reduce the number of transactions per second.

Answer

Enable Multi-AZ on the cluster.

Question 14

A database administrator notices that an Amazon RDS for MySQL instance is using 100% of its allocated storage. Which action should be taken first to prevent the instance from becoming inaccessible?

Accepted Answer

Modify the DB instance to increase allocated storage.. When an Amazon RDS for MySQL instance reaches 100% storage utilization, the most immediate action to prevent it from becoming inaccessible is to modify the DB instance to increase allocated storage. This adds storage capacity and allows normal operations to continue. Option B (snapshot and archive to S3) does not free up storage on the instance. Option C (deleting old binary logs) can free space but is not guaranteed to free enough and may not be a long-term solution; also, binary logs are needed for replication and point-in-time recovery. Option D (reboot) does not resolve the storage shortage.

Answer

Create a snapshot and archive it to Amazon S3.

Answer

Delete old binary logs to free up space.

Answer

Reboot the DB instance.

Question 15

A developer receives a 'ResourceNotFoundException' when trying to describe a DynamoDB table. The developer runs the command shown in the exhibit and gets the output. What is the most likely cause?

Accepted Answer

The developer is using a different AWS region or the table name has incorrect case.. The 'ResourceNotFoundException' indicates the table was not found. The command output lists tables in a specific region. If the table exists in another region, it will not appear. Additionally, DynamoDB table names are case-sensitive. Option A correctly identifies these as the most likely causes. Option B is incorrect because a table not in ACTIVE state would generate a different error. Option C is unlikely because the describe command uses the table name, not the ARN. Option D is incorrect because the describe command succeeded (returned a list), but the specific table was not found due to region or case mismatch.

Answer

The table is not in ACTIVE state.

Answer

The table ARN is incorrect.

Answer

The developer does not have permission to describe the table.