DBS-C01 Mock Exam 73 — 25 Questions

Question 1

A company is deploying a multi-region application with Amazon Aurora Global Database. They need to ensure that the secondary region can be promoted to primary with minimal data loss in the event of a regional failure. Which configuration should they use?

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

Accepted Answer

Deploy Amazon Aurora Global Database with one primary Region and up to five secondary Regions.. Amazon Aurora Global Database is designed for low-latency cross-Region replication and provides a managed failover capability that promotes a secondary Region to primary with a Recovery Point Objective (RPO) of typically less than 1 second. This configuration meets the requirement of minimal data loss during a regional failure because replication is done at the storage layer, not through asynchronous binlog replication, ensuring near-zero lag.

Answer

Deploy Amazon Aurora Serverless with cross-Region replication.

Answer

Deploy Amazon RDS for MySQL with cross-Region read replicas.

Answer

Deploy Amazon RDS for PostgreSQL with Multi-AZ and cross-Region snapshot copy.

Question 2

Which TWO of the following are valid strategies for reducing costs for an Amazon DynamoDB table with on-demand capacity mode? (Choose TWO.)

Accepted Answer

Implement DynamoDB Accelerator (DAX) to cache reads.. Implementing DAX reduces the number of read requests to the underlying DynamoDB table by serving cached results, which lowers read capacity consumption and thus reduces costs for on-demand tables. Switching to provisioned capacity with auto scaling allows you to pay for a baseline of read/write capacity units rather than per-request pricing, which is more cost-effective for predictable or steady workloads.

Answer

Use Amazon DynamoDB TTL to automatically delete expired data.

Answer

Enable DynamoDB global tables to distribute traffic.

Answer

Use DynamoDB Streams to process updates asynchronously.

Question 3

A company is using Amazon ElastiCache for Redis as a caching layer for a web application. The application team reports that cache miss rates have increased significantly, causing higher database load. The Redis cluster has two nodes (one primary, one replica) with the default eviction policy of noeviction. Which action should the database specialist recommend to reduce cache misses?

Accepted Answer

Change the eviction policy to allkeys-lru to allow Redis to evict less recently used keys.. Changing the eviction policy to allkeys-lru allows Redis to evict less recently used keys when memory is full, reducing cache misses. Option A is incorrect because simply increasing memory does not change the eviction policy; with noeviction, writes will fail when memory is full. Option C is incorrect because enabling AOF persistence improves durability but does not affect cache misses. Option D is incorrect because adding read replicas distributes read traffic but does not reduce cache misses if the keys are not in the cache.

Answer

Increase the memory of existing nodes to accommodate more keys.

Answer

Enable AOF persistence to improve cache durability.

Answer

Add more read replicas to distribute the cache load.

Question 4

A company is using Amazon DynamoDB with on-demand capacity. The operations team wants to monitor for throttled read requests. Which metric from Amazon CloudWatch should be used to set up an alarm for read throttling?

Accepted Answer

ReadThrottleEvents. 'ReadThrottleEvents' is a CloudWatch metric that directly indicates throttled read requests on a DynamoDB table. For write throttling, the correct metric is 'WriteThrottleEvents', but it is not among the options given. Therefore, only one option correctly answers the question as revised.

Answer

ConsumedWriteCapacityUnits

Answer

ThrottledPutRecords

Answer

ProvisionedReadCapacityUnits

Answer

ThrottledGetRecords

Question 5

A financial services company needs a database to store transaction records with strict ACID compliance and the ability to run complex JOIN queries for reporting. The workload is read-heavy with occasional batch inserts. Which AWS database service should they choose?

Accepted Answer

Amazon RDS for PostgreSQL. Amazon RDS for PostgreSQL is the correct choice because it provides full ACID compliance through its support for PostgreSQL's MVCC (Multi-Version Concurrency Control) and WAL (Write-Ahead Logging), ensuring transactional integrity for financial transaction records. It also excels at complex JOIN queries for reporting, leveraging PostgreSQL's advanced query optimizer and support for foreign keys, indexes, and CTEs. The read-heavy workload with occasional batch inserts is well-suited to RDS for PostgreSQL, as it can scale read replicas and handle batch operations efficiently with proper indexing.

Answer

Amazon DynamoDB

Answer

Amazon Aurora Serverless

Answer

Amazon Timestream

Question 6

Which THREE actions should be taken to prepare for a migration of an on-premises MySQL database to Amazon RDS for MySQL with minimal downtime using AWS DMS?

Accepted Answer

Enable binary logging on the source MySQL database. AWS DMS requires binary logging (binlog) to be enabled on the source MySQL database for ongoing replication (change data capture). DMS reads the binary log to capture inserts, updates, and deletes in near real-time, which is essential for minimizing downtime during migration.

Answer

Disable foreign key checks on the source database

Answer

Take a full backup of the source database

Question 7

A company is migrating a 2 TB Oracle database to Amazon Aurora PostgreSQL. The on-premises database is 2 TB and the network link is 1 Gbps. The migration must complete within 48 hours with minimal data loss. The DBA has extracted the schema using AWS SCT and created an Aurora cluster. The DBA now needs to transfer the data. The DBA tried using AWS DMS over the network but estimates it will take 72 hours due to network overhead. The DBA also considered using an AWS Snowball Edge device but is concerned about the time to order and ship the device. Which approach should the DBA take to meet the deadline?

Accepted Answer

Use AWS Snowball Edge to transfer the database dump and then use DMS for change data capture. It combines the speed of Snowball Edge for the initial bulk data transfer (2 TB) with AWS DMS for ongoing change data capture (CDC) to minimize data loss. Although ordering and shipping a Snowball device takes time, once received, the data transfer is much faster than over a 1 Gbps network, which would take over 48 hours. DMS alone (option A) is estimated to take 72 hours, exceeding the deadline. Option B (S3 upload) still relies on network speed and would be too slow. Option D (full load only) abandons CDC and does not meet the minimal data loss requirement.

Answer

Use AWS DMS with change data capture and optimize the network by enabling compression

Answer

Use AWS S3 to upload the database dump and then load into Aurora

Answer

Use AWS DMS to perform a full load and then stop replication, accepting some data loss

Question 8

A company is migrating its on-premises Oracle database to Amazon RDS for Oracle. The database is 2 TB in size and has a 24-hour maintenance window. The company needs to minimize downtime during the migration. Which AWS service should be used to perform the migration with minimal downtime?

Accepted Answer

AWS Database Migration Service. AWS Database Migration Service (AWS DMS) can migrate the on-premises Oracle database to Amazon RDS for Oracle with minimal downtime by using ongoing replication. Option B (Oracle Data Guard) is not supported for cross-environment replication to Amazon RDS. Option C (AWS Schema Conversion Tool) is used for schema conversion, not data migration. Option D (AWS Data Pipeline) is a data orchestration service unrelated to database migration.

Answer

Oracle Data Guard

Answer

AWS Schema Conversion Tool (AWS SCT)

Answer

AWS Data Pipeline

Question 9

A company is deploying an Amazon DynamoDB table with server-side encryption using a customer-managed AWS KMS key. The security team requires that the key be automatically rotated every year and that access to the key be logged. Which THREE steps should be taken?

Accepted Answer

Enable automatic key rotation for the KMS key.. To meet the requirements: (1) Enable automatic key rotation (Option A) to satisfy the automatic rotation requirement. (2) Enable AWS CloudTrail to log KMS API calls (Option C) to log access to the key. (3) Create a KMS key policy that restricts usage to specific IAM roles (Option D) to control access. Option B is incorrect because AWS CloudHSM is a hardware security module, not used for KMS key rotation or logging. Option E is incorrect because client-side encryption is not relevant; server-side encryption with KMS is already used.

Answer

Use AWS CloudHSM to store the key and manage rotation.

Answer

Configure the DynamoDB table to use client-side encryption.

Question 10

A company is using Amazon DynamoDB with global tables to support a multi-region application. They notice that writes to the table in us-east-1 are not replicating to the table in eu-west-1. The replication lag metric shows increasing values. What is the most likely cause?

Accepted Answer

The table in eu-west-1 has been removed as a replica region from the global table configuration.. If the replica region (eu-west-1) has been removed from the global table configuration, DynamoDB will stop replicating writes to that region, and the replication lag metric will show increasing values. Option A is incorrect: while a lower write capacity in eu-west-1 could cause throttling and replication lag, it would not completely stop replication; the lag metric would still show some activity. Option B is incorrect: DynamoDB Streams must be enabled on the source table for global tables to function, but disabling them would halt replication entirely, not cause increasing lag. Option C is incorrect: global tables replicate asynchronously over DynamoDB's internal network and do not require VPC connectivity between regions.

Answer

The table in eu-west-1 has a lower write capacity and is throttling incoming writes.

Answer

DynamoDB Streams is disabled on the table in us-east-1.

Answer

The DynamoDB table in us-east-1 is not accessible from eu-west-1 due to VPC restrictions.

Question 11

A company is designing a database for a social media analytics platform that requires: 1) storing relationships between users, posts, and interests; 2) running complex graph queries like 'find all friends of friends who like topic X'; 3) high availability with multi-region replication. Which TWO AWS services should they consider? (Choose TWO.)

Accepted Answer

Amazon Neptune. Amazon Neptune is a fully managed graph database service optimized for storing and querying highly connected data, such as user, post, and interest relationships. It supports property graph and RDF models, enabling complex graph queries like 'find all friends of friends who like topic X' using Gremlin or SPARQL. This directly satisfies the requirement for graph query capabilities. Amazon Aurora Global Database provides multi-region replication with low-latency global read operations and automatic failover, meeting the high availability and multi-region replication requirement. Together, Neptune handles the graph query workload, while Aurora Global Database provides the global distribution and disaster recovery needed for the analytics platform.

Answer

Amazon Redshift

Answer

Amazon DynamoDB with Global Tables

Answer

Amazon ElastiCache for Redis

Question 12

A database specialist is troubleshooting a performance issue on an Amazon Aurora MySQL DB cluster. The cluster has a primary instance and two Aurora Replicas. The application is experiencing high read latency. Which THREE actions should the specialist take to identify the cause?

Accepted Answer

Check the Performance Insights for the Aurora Replicas to identify long-running queries.. Performance Insights provides a detailed view of database load, including wait events, SQL queries, and host-level metrics, which can pinpoint long-running queries causing high read latency on the Aurora Replicas. By analyzing the top SQL statements and their execution plans, the specialist can identify inefficient queries or contention issues that degrade read performance.

Answer

Check the Write Latency metric on the primary instance.

Answer

Increase the instance size of the Aurora Replicas.

Question 13

A company is running an Amazon RDS for MySQL instance with Multi-AZ. The primary instance in us-east-1a fails, and the standby in us-east-1b is promoted. The application cannot connect after failover. Which TWO steps should the database administrator take to restore connectivity?

Accepted Answer

Update the application's connection string to point to the new writer endpoint.. After failover, the application may be connecting to the old primary instance endpoint. Updating the connection string to the DNS writer endpoint (which automatically points to the new primary) ensures connectivity. Option D is correct because after failover, the writer endpoint's DNS record updates to the new primary's IP. Waiting for propagation and flushing the DNS cache ensures the application resolves the updated IP. Option B is incorrect because rebooting is not required and would cause further disruption. Option C is incorrect because the security group already permits traffic from the application; the issue is DNS resolution, not network access. Option E is incorrect because creating a read replica does not solve the connectivity issue and is unnecessary for a Multi-AZ failover.

Answer

Reboot the new primary instance to reset connections.

Answer

Update the security group to allow inbound traffic from the application.

Answer

Create a read replica and promote it to a new primary.

Question 14

A company is deploying a new Amazon DynamoDB table with on-demand capacity. The table will store session data for a web application. Which THREE features should be enabled to improve performance and durability?

Accepted Answer

DynamoDB Accelerator (DAX). For an on-demand DynamoDB table, Auto scaling is not applicable because on-demand mode automatically scales throughput. To improve performance, use DynamoDB Accelerator (DAX) which provides an in-memory cache for microsecond read latency. For durability, enable Point-in-time recovery (PITR) for continuous backups and Global tables for multi-region replication, which also provides disaster recovery and low-latency global reads. Time to Live (TTL) helps manage data lifecycle but does not directly improve performance or durability.

Answer

Auto scaling

Answer

Time to Live (TTL)

Question 15

A company uses Amazon DynamoDB with fine-grained access control using IAM policies. A developer reports that an application role can read and write to the 'orders' table but cannot perform a Scan operation on a Global Secondary Index (GSI). The IAM policy attached to the role includes 'dynamodb:Scan' and the resource ARN for the table. What is the likely reason for this failure?

Accepted Answer

The IAM policy does not include the GSI's ARN in the resource statement.. DynamoDB Global Secondary Indexes (GSIs) have their own Amazon Resource Names (ARNs) separate from the base table. When using IAM policies with fine-grained access control, the policy must explicitly include the ARN of the GSI in the resource statement to allow operations like Scan on that GSI. Without the GSI ARN, the Scan operation on the GSI is denied by default, even if the policy allows 'dynamodb:Scan' on the base table. Option A is incorrect because the policy does not mention time-of-day conditions. Option B is incorrect because the role can read from the base table, but the issue is with the GSI. Option D is incorrect because the action 'dynamodb:Scan' is allowed on the table but not on the GSI.

Answer

The policy has a condition that restricts Scan operations based on the time of day.

Answer

The role does not have permission to read from the base table.

Answer

The IAM policy does not allow the 'dynamodb:Scan' action on the table.

Question 16

A company is migrating its on-premises Oracle database to Amazon RDS for Oracle. The database is 2 TB in size and contains both transactional and analytical workloads. The company uses Oracle Data Pump for migration. During the migration, the database specialist notices that the export job on the source database is taking longer than expected and is generating significant I/O, impacting production performance. The company needs to minimize the impact on the source database while completing the migration within a 48-hour window. The source database is currently running on a dedicated server with sufficient CPU and memory. Which course of action should the database specialist take?

Accepted Answer

Use Oracle Data Pump in network_link mode to directly import the data from the source to the target RDS instance without intermediate files.. Oracle Data Pump's network_link mode allows the source database to export data directly to the target RDS for Oracle instance over a database link, bypassing the need to write intermediate dump files to disk. This eliminates the I/O overhead on the source server's storage subsystem, which is the primary cause of the production performance impact, while still completing the migration within the 48-hour window.

Answer

Use AWS Database Migration Service (AWS DMS) with full load and change data capture (CDC) to migrate the database.

Answer

Use Data Pump to export to a networked file system (NFS) mount point to offload storage I/O to the network.

Answer

Increase the parallel workers for the Data Pump export job to 8 to speed up the export and reduce the time window.

Question 17

A database administrator is troubleshooting an Amazon RDS for PostgreSQL DB instance that is experiencing high CPU utilization. The administrator runs the following query to find the current running queries:

SELECT pid, now() - pg_stat_activity.query_start AS duration, query, state
FROM pg_stat_activity
WHERE state = 'active';

The output shows a high number of queries with a state of 'active' and durations exceeding several minutes. What should the administrator do FIRST to reduce CPU utilization?

Accepted Answer

Use pg_terminate_backend to terminate the long-running queries.. The immediate cause of high CPU utilization is the long-running active queries consuming resources. Using pg_terminate_backend to terminate these queries will quickly free up CPU cycles, providing immediate relief. This is the first troubleshooting step before making configuration changes or scaling, as it directly addresses the symptom shown in the pg_stat_activity output.

Answer

Modify the max_connections parameter to limit concurrent sessions.

Answer

Scale up the DB instance to a larger instance class.

Answer

Enable pg_stat_statements to collect query performance data.

Question 18

Which THREE factors should be considered when planning a cross-Region disaster recovery strategy for an Amazon Aurora MySQL DB cluster? (Choose 3.)

Accepted Answer

Network latency between source and target Regions.. Network latency between source and target Regions directly impacts the replication lag for Amazon Aurora Global Database. Aurora uses asynchronous replication across Regions, and higher latency increases the delay between committing a transaction on the primary cluster and it being available on the secondary cluster, which affects the achievable Recovery Point Objective (RPO).

Answer

Provisioned IOPS for the primary cluster.

Answer

Failover priority of reader instances.

Question 19

A company is using Amazon RDS for MySQL. They want to audit all database logins and failed login attempts. Which option should they enable?

Accepted Answer

Set the parameter audit_log = 'ON' in the DB parameter group.. Setting the parameter audit_log = 'ON' enables audit logging for MySQL, which logs connections and disconnections, including failed login attempts. Option A is wrong because log_queries_not_using_indexes logs queries that do not use indexes, not login attempts. Option C is wrong because general_log logs all queries, not just logins. Option D is wrong because slow_query_log logs only slow queries.

Answer

Set the parameter log_queries_not_using_indexes = 'ON' in the DB parameter group.

Answer

Set the parameter general_log = 'ON' in the DB parameter group.

Answer

Set the parameter slow_query_log = 'ON' in the DB parameter group.

Question 20

A company is migrating an on-premises MongoDB database to Amazon DocumentDB. The migration must have minimal downtime. Which THREE steps should be taken? (Choose three.)

Accepted Answer

Create an Amazon DocumentDB cluster as the target.. You must create the target DocumentDB cluster before migration. Option C is correct: AWS DMS can perform a full load followed by ongoing replication to minimize downtime. Option E is correct: the source MongoDB must be configured to capture oplog events so that DMS can replicate changes. Option A is incorrect because AWS Snowball Edge is for offline data transfer, which would not achieve minimal downtime. Option D is incorrect because sharding the cluster across multiple regions is not required for a migration with minimal downtime.

Answer

Use AWS Snowball Edge to transfer initial data.

Answer

Shard the DocumentDB cluster across multiple regions.