DBS-C01 Practice Exam 56 — 20 Questions

Question 1

A company uses Amazon DynamoDB as the primary database for a global gaming application. The application requires single-digit millisecond latency for user profile lookups by user ID. However, some queries need to retrieve all active users in a region (e.g., 'us-east-1') for administrative dashboards, and these queries currently perform full table scans, causing high costs and throttling. What design approach should be taken to optimize this?

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

Accepted Answer

Create a global secondary index (GSI) on the region attribute.. Creating a Global Secondary Index (GSI) on the 'region' attribute allows the administrative dashboard queries to retrieve all active users in a specific region using an efficient index scan instead of a full table scan. This reduces read capacity consumption, avoids throttling, and maintains single-digit millisecond latency for the indexed queries, while the base table remains optimized for user ID lookups.

Answer

Implement DynamoDB Accelerator (DAX) to cache the dashboard queries.

Answer

Increase the read capacity units (RCUs) on the base table.

Answer

Create a local secondary index (LSI) on the region attribute.

Question 2

A company is migrating a 1 TB Oracle database to Amazon Aurora PostgreSQL using AWS DMS. They need to ensure minimal downtime and data consistency. Which TWO actions should the company take?

Accepted Answer

Enable change data capture (CDC) on the source Oracle database. Enabling Change Data Capture (CDC) on the source Oracle database allows AWS DMS to capture ongoing changes after the full load, enabling a near-zero downtime migration by continuously replicating transactions to the target Aurora PostgreSQL. Option C is correct because enabling data validation on the DMS task ensures that the data migrated is consistent between the source and target, verifying that no data loss or corruption occurred during the migration process.

Answer

Increase the target Aurora storage to 2 TB to avoid storage issues

Answer

Disable foreign key constraints on the target during migration

Answer

Use AWS Schema Conversion Tool to convert the schema

Question 3

A company is planning to migrate a 5 TB Oracle data warehouse to Amazon Redshift. They need to transform the data during migration. Which AWS service should they use to perform the transformation?

Accepted Answer

AWS Glue to perform extract, transform, and load (ETL) jobs.. AWS Glue is the correct choice because it is a fully managed ETL service designed for data transformation and loading into Amazon Redshift. It can handle the 5 TB Oracle data warehouse migration by running Spark-based ETL jobs that transform the data before writing it to Redshift, making it ideal for batch-oriented data warehouse migrations.

Answer

Amazon Kinesis Data Analytics for real-time transformation.

Answer

Amazon Athena to query the source data and write results to Redshift.

Answer

AWS Database Migration Service (DMS) with transformation rules.

Question 4

A database administrator is troubleshooting connectivity to an Amazon RDS for MySQL DB instance. The application is running on an EC2 instance in the same VPC and security group. The application can connect using the endpoint shown in the exhibit. However, the security team requires that all connections be encrypted using SSL. The DBA has enabled SSL on the DB instance and modified the parameter group to set require_secure_transport to ON. The application is now failing to connect. What is the most likely cause?

Accepted Answer

The application's JDBC connection string does not include SSL parameters such as useSSL=true.. When `require_secure_transport` is set to ON, the MySQL server rejects any connection that does not use SSL/TLS. The application's JDBC connection string must include SSL parameters such as `useSSL=true` (or `sslMode=REQUIRED` in newer drivers) to initiate an encrypted connection. Without these parameters, the connection attempt fails because the server requires secure transport. This is the most likely cause of the failure after enabling SSL enforcement.

Answer

The DB instance endpoint is not resolving to the correct IP address.

Answer

The database user account does not have the SSL privilege granted.

Answer

The security group does not allow inbound traffic on port 3307, which is used for SSL connections.

Question 5

A gaming company uses Amazon DynamoDB to store player profiles. Each profile is about 5 KB and is accessed frequently. The access pattern is mostly point reads by player ID. The company wants to reduce read costs while maintaining low latency. Currently, the table uses provisioned capacity with 3000 RCU. Which change would be MOST effective?

Accepted Answer

Use DynamoDB Accelerator (DAX) to cache frequently accessed items.. DynamoDB Accelerator (DAX) provides an in-memory cache that can serve frequently accessed items (like player profiles) with microsecond latency, reducing the number of read requests that hit the underlying table. Since each profile is 5 KB and accessed via point reads, DAX can absorb a significant portion of the read traffic, allowing you to lower provisioned RCU without sacrificing performance. This directly reduces read costs while maintaining low latency, making it the most effective solution.

Answer

Use strongly consistent reads instead of eventually consistent reads.

Answer

Switch from provisioned capacity to on-demand capacity mode.

Answer

Decrease the provisioned RCU to 2000 and rely on adaptive capacity.

Question 6

A startup wants to store session data for a web application. Each session is small (under 1 KB) and accessed frequently with low latency. The data can be ephemeral and does not require complex queries. Which AWS database service is most suitable?

Accepted Answer

Amazon ElastiCache for Redis. Amazon ElastiCache for Redis is the most suitable choice because it is an in-memory data store that provides sub-millisecond latency for frequent reads and writes, ideal for ephemeral session data under 1 KB. Redis supports key-value storage with built-in time-to-live (TTL) expiration, which automatically removes stale sessions without additional application logic, and its simple data model avoids the overhead of complex queries.

Answer

Amazon DynamoDB

Answer

Amazon RDS for PostgreSQL

Answer

Amazon Neptune

Question 7

A company wants to migrate its on-premises Oracle database to Amazon Aurora PostgreSQL. The company needs to convert the database schema and code from Oracle to PostgreSQL. Which AWS service should they use for schema conversion?

Accepted Answer

AWS Schema Conversion Tool (SCT). AWS Schema Conversion Tool (SCT) is the correct choice because it is specifically designed to convert database schemas, stored procedures, functions, and other code objects from one database engine to another, such as Oracle to Amazon Aurora PostgreSQL. It analyzes the source schema and generates a target schema with equivalent PostgreSQL syntax, handling data type mappings, PL/SQL to PL/pgSQL conversion, and other compatibility issues. AWS DMS handles data migration but does not perform schema or code conversion.

Answer

AWS DMS

Answer

AWS Glue

Answer

AWS Database Migration Service

Question 8

A company needs to migrate a 100 GB MongoDB database to Amazon DocumentDB (with MongoDB compatibility). The migration must have minimal impact on the source database performance. Which approach should the company take?

Accepted Answer

Use AWS Database Migration Service (AWS DMS) with ongoing replication from the MongoDB source.. AWS DMS with ongoing replication is the correct approach because it supports continuous change data capture (CDC) from MongoDB, enabling a live migration with minimal performance impact on the source. DMS reads the MongoDB oplog to capture changes without locking the database, which is critical for a 100 GB production database. This allows the target DocumentDB to stay synchronized until cutover, reducing downtime and avoiding the need for a full export/import that would strain the source.

Answer

Use AWS DataSync to transfer the MongoDB data files.

Answer

Set up a MongoDB replica set on Amazon EC2 and promote it to primary, then migrate to DocumentDB.

Answer

Use mongodump to export the data and mongorestore to import into DocumentDB.

Question 9

A company is using Amazon Redshift for data warehousing. The query performance has degraded over time. The DBA suspects that the distribution style of large tables is suboptimal. Which Redshift system view should be queried to identify distribution skew?

Accepted Answer

SVV_DISKUSAGE. SVV_DISKUSAGE provides disk usage per slice, which helps identify distribution skew. Option A is wrong because STL_SCAN provides details about scan operations, not skew. Option B is wrong because PG_TABLE_DEF shows table definitions, not skew. Option D is wrong because STV_TBL_PERM shows storage usage per table but not per slice, making it less suitable for skew analysis.

Answer

STL_SCAN

Answer

PG_TABLE_DEF

Answer

STV_TBL_PERM

Question 10

A company is migrating an on-premises MongoDB database to AWS. They need a managed database service that is compatible with MongoDB and supports automated backups, scaling, and high availability. Which service should they use?

Accepted Answer

Amazon DocumentDB. Amazon DocumentDB is a fully managed, MongoDB-compatible document database service designed for workloads that require MongoDB's document model, query patterns, and APIs. It supports automated backups (continuous backups to S3 with point-in-time recovery), automatic scaling of storage and compute, and multi-AZ high availability with synchronous replication across three Availability Zones, making it the correct choice for migrating an on-premises MongoDB database to a managed AWS service.

Answer

Amazon DynamoDB

Answer

Amazon RDS for MySQL

Answer

Amazon Neptune

Question 11

A company runs an e-commerce platform using Amazon Aurora MySQL with Multi-AZ deployment. The application has a read-heavy workload and uses a mix of SELECT and UPDATE queries. Recently, the company migrated from a db.r5.large to a db.r5.2xlarge instance class to handle increased traffic. However, after the migration, the CPU utilization remains high during peak hours, and the application's page load times have increased. The DBA notices that the 'Read IOPS' metric is high, but the 'Read Latency' metric is low. There is also a high number of 'Select' queries in the database. The application uses a single database endpoint. What should the DBA do to reduce CPU utilization and improve read performance?

Accepted Answer

Create one or more Aurora Replicas and modify the application to use read-only endpoints for SELECT queries.. Creating Aurora Replicas offloads read-only SELECT queries from the primary instance, reducing CPU utilization on the primary and improving overall read throughput. Option A is incorrect because enabling Multi-AZ with one standby replica provides high availability but does not help with read scaling; the standby is not used for reads. Option B is incorrect because Performance Insights is a monitoring tool that helps identify performance bottlenecks but does not directly reduce CPU utilization. Option C is incorrect because simply upgrading to a larger instance class may temporarily alleviate the issue but is not cost-effective and does not address the root cause of read-heavy workload imbalance; adding read replicas scales reads horizontally.

Answer

Enable Multi-AZ with one standby replica.

Answer

Enable Performance Insights and analyze the top SQL.

Answer

Upgrade the instance class to db.r5.4xlarge.

Question 12

A company is planning to migrate a 5 TB Oracle data warehouse to Amazon Redshift. The migration must be completed within a 2-day maintenance window. The source database is heavily normalized and uses complex joins. Which strategy is most appropriate?

Accepted Answer

Use AWS SCT to convert the Oracle schema to Redshift-compatible format, then use AWS DMS to load the data.. AWS Schema Conversion Tool (SCT) is specifically designed to convert Oracle schemas (including heavily normalized structures with complex joins) into Amazon Redshift-compatible format, which is essential for a data warehouse migration. AWS DMS then efficiently loads the converted schema and data into Redshift within the 2-day window, as it can handle large volumes with full load and ongoing replication if needed.

Answer

Use AWS DMS to directly migrate data to Redshift with full load and ongoing replication.

Answer

Export data to flat files, use S3 Transfer Acceleration to upload to S3, then COPY into Redshift.

Answer

Use AWS Glue to crawl the Oracle schema and create Redshift tables, then run a Glue ETL job to load data.

Question 13

A developer needs to restore an Amazon RDS for PostgreSQL DB instance to a specific point in time within the retention period. What must be enabled for this operation to be possible?

Accepted Answer

Automated backups with a retention period greater than 0.. Point-in-time recovery (PITR) on Amazon RDS relies on automated backups plus transaction logs. If automated backups are disabled or the retention period is set to 0, PITR is not possible — you can only restore from a manual snapshot, which restores to the snapshot time, not an arbitrary point. Therefore, automated backups with retention > 0 must be enabled.

Answer

Deletion protection enabled.

Answer

A read replica in the same region.

Answer

Multi-AZ deployment.

Question 14

Which TWO of the following are benefits of using Amazon DynamoDB Accelerator (DAX)? (Choose 2.)

Accepted Answer

Reduces read latency to microseconds for cached items. Option C is correct because DAX is an in-memory cache that sits in front of DynamoDB and serves cached item reads in microseconds, dramatically lowering read latency compared to the single-digit millisecond latency of direct DynamoDB reads. Option E is correct because when reads are served from the DAX cache, they do not hit the underlying DynamoDB table, so fewer read capacity units (RCUs) are consumed on the table. Option A is not a DAX benefit because DAX is a read-through/write-through cache that does not improve write throughput by caching writes; writes still go to DynamoDB. Option B is incorrect because DAX does not compress data to reduce storage costs; it caches items in memory. Option D is incorrect because automatic scaling of write capacity is handled by DynamoDB auto scaling, not by DAX.

Answer

Improves write throughput by caching write operations

Answer

Reduces storage costs by compressing data

Answer

Automatically scales write capacity based on demand

Question 15

Refer to the exhibit. A database administrator runs the AWS CLI command shown. The output is: ["available", false]. What does this output indicate about the DB instance?

Accepted Answer

The DB instance is available and is not configured for Multi-AZ.. The output ["available", false] from the AWS CLI command (likely describing a DB instance) indicates that the DB instance status is 'available' and the MultiAZ field is false, meaning it is not configured for Multi-AZ. Thus, the instance is available and not in a Multi-AZ deployment.

Answer

The DB instance is in the process of being modified to enable Multi-AZ.

Answer

The DB instance is in a Multi-AZ deployment and is available.

Answer

The DB instance is stopped and is not in a Multi-AZ configuration.

Question 16

A company is migrating a 2 TB MySQL database to Amazon Aurora MySQL. They want to minimize downtime and ensure data consistency. Which TWO methods should they use? (Choose two.)

Accepted Answer

Use AWS DMS with ongoing replication. Option A is correct because AWS Database Migration Service (AWS DMS) with ongoing replication (change data capture) performs a full load followed by continuous replication of changes from the source MySQL database to Aurora MySQL, allowing the cutover to happen with minimal downtime. Option D is correct because binary logging (log_bin) must be enabled on the source MySQL instance so that DMS can read the binary log and capture ongoing changes for CDC; without it, ongoing replication cannot function. Together, DMS plus binary logging enable a low-downtime, consistent migration. Option B is not needed because AWS SCT is for converting heterogeneous schemas (for example, Oracle or SQL Server to MySQL), whereas this is a homogeneous MySQL-to-Aurora MySQL migration. Option C is inappropriate because Snowball Edge is for offline bulk data transfer, which would require downtime and does not provide ongoing replication. Option E is incorrect because mysqldump produces a static export that cannot keep the target in sync during the migration, causing significant downtime.

Answer

Use AWS Schema Conversion Tool to convert the schema

Answer

Use AWS Snowball Edge to transfer backup files

Answer

Use mysqldump to export data

Question 17

A company is using Amazon DynamoDB for a gaming leaderboard application. Recently, users have experienced increased latency when updating scores. The DynamoDB table has on-demand capacity mode. The application performs UpdateItem calls with a condition expression. Which action is most likely to reduce the latency?

Accepted Answer

Ensure that there are no throttled requests in the CloudWatch metrics and verify that the table is not experiencing hot partitions.. Increased latency in DynamoDB can be caused by hot partitions where many requests hit the same partition, leading to throttling even with on-demand capacity if the partition limits are exceeded. Checking CloudWatch metrics for throttled requests and partition metrics helps identify hot partitions. Option A is incorrect because adding a GSI does not improve UpdateItem performance; it only helps query performance. Option B is incorrect: on-demand mode already handles capacity, and increasing read capacity units does not affect write operations like UpdateItem. Option C is incorrect: disabling conditional writes would break the application's concurrency control and does not guarantee latency reduction; condition evaluation is a fast, internal operation.

Answer

Add a global secondary index (GSI) with the score as the sort key to improve update performance.

Answer

Switch the table to provisioned capacity and increase the read capacity units to handle peak load.

Answer

Disable conditional writes to reduce the overhead of condition expression evaluation.

Question 18

Refer to the exhibit. A developer reports that the RDS MySQL instance 'mydb' is experiencing high write latency. The storage is gp2 with 100 GB. What is the MOST likely cause of the write latency?

Accepted Answer

The gp2 volume size is too small, resulting in insufficient baseline IOPS. The gp2 volume's baseline IOPS are determined by the volume size at a ratio of 3 IOPS per GB, up to 16,000 IOPS. With a 100 GB gp2 volume, the baseline IOPS is only 300 (100 × 3). This is insufficient for write-heavy workloads, causing write latency as the volume exhausts its IOPS credit balance and enters a throttled state. Burst credits can temporarily boost performance, but sustained high write throughput will deplete credits and lead to latency.

Answer

There is a read replica causing replication lag

Answer

The instance class db.r5.large does not provide enough memory

Answer

Multi-AZ is not enabled, causing synchronous replication overhead

Question 19

A company wants to encrypt an existing unencrypted Amazon RDS for SQL Server instance. What is the MOST efficient way to achieve this?

Accepted Answer

Create a snapshot of the DB instance and copy it with encryption enabled. Restore the snapshot to a new encrypted instance.. You cannot directly enable encryption on an existing unencrypted RDS instance. The most efficient method is to take a snapshot of the instance, copy it with encryption enabled (which re-encrypts the data using AWS KMS), and then restore that snapshot to a new encrypted DB instance. This approach minimizes downtime and leverages native RDS snapshot capabilities without requiring external tools.

Answer

Create a read replica with encryption enabled.

Answer

Modify the DB instance to enable encryption.

Answer

Use AWS DMS to migrate data to a new encrypted instance.

Question 20

A company wants to migrate an on-premises SQL Server database to Amazon RDS for SQL Server. They need to convert stored procedures and functions. Which AWS service should they use?

Accepted Answer

AWS SCT. AWS SCT (Schema Conversion Tool) is the correct service because it specializes in converting database schemas, including stored procedures and functions, from one engine to another. For migrating on-premises SQL Server to Amazon RDS for SQL Server, SCT can analyze and convert the schema objects, handling syntax differences and compatibility issues automatically.

Answer

AWS CloudEndure Migration

Answer

AWS DMS

Answer

AWS Snowball