DBS-C01 Practice Test 20 — 15 Questions

Question 1

Which THREE factors should be considered when designing a database for a high-traffic web application that requires low-latency reads and writes?

Accepted Answer

Caching layer. A caching layer (e.g., Amazon ElastiCache for Redis or Memcached) reduces read latency by serving frequently accessed data from in-memory stores, offloading the primary database. For high-traffic web applications, this minimizes disk I/O and improves response times for both reads and writes when combined with write-through or write-behind strategies.

Answer

Strict normalization

Answer

Denormalization of data

Question 2

A company wants to migrate its Oracle data warehouse to Amazon Redshift. The source database is 10 TB and has many complex stored procedures. Which AWS service should be used primarily for converting the stored procedures to Amazon Redshift compatible code?

Accepted Answer

AWS Schema Conversion Tool (AWS SCT). AWS Schema Conversion Tool (AWS SCT) is the correct choice because it is specifically designed to convert database schemas and complex code objects, such as stored procedures, functions, and packages, from one database engine to another. For an Oracle-to-Amazon Redshift migration, AWS SCT can automatically translate Oracle PL/SQL stored procedures into Amazon Redshift compatible SQL (e.g., using PL/pgSQL or SQL functions), handling syntax differences and unsupported features. This makes it the primary tool for converting the 10 TB data warehouse's stored procedures, whereas other services focus on data movement or ETL, not schema and code conversion.

Answer

AWS Glue

Answer

AWS Database Migration Service (AWS DMS)

Answer

Amazon Redshift COPY command

Question 3

A company is migrating a 500 GB Oracle database to Amazon Aurora PostgreSQL. They need to convert the schema and migrate the data. The application uses Oracle-specific features like hierarchical queries and stored procedures. Which combination of services should they use?

Accepted Answer

Use AWS Schema Conversion Tool (SCT) to convert the schema and AWS Database Migration Service (DMS) to migrate the data.. AWS SCT converts Oracle-specific schema objects (including hierarchical queries and stored procedures) to PostgreSQL-compatible code, while AWS DMS handles the ongoing data migration with minimal downtime. This combination is the standard AWS approach for heterogeneous database migrations, as SCT addresses schema conversion and DMS handles data transfer.

Answer

Use AWS Snowball Edge to transfer the database files and then use SCT to convert the schema.

Answer

Use AWS Database Migration Service (DMS) with the Oracle as source and Aurora PostgreSQL as target.

Answer

Use AWS Schema Conversion Tool (SCT) to convert the schema and then manually export/import data.

Question 4

A company is migrating an on-premises Oracle database to Amazon RDS for Oracle. They need to minimize downtime. Which TWO actions should they take?

Accepted Answer

Set up AWS DMS with change data capture (CDC) from the source. AWS DMS with change data capture (CDC) enables continuous replication of ongoing changes from the source Oracle database to the target RDS instance. This allows the source to remain fully operational during the bulk load phase and then switch over with minimal downtime, as only the final CDC catch-up is needed before cutover.

Answer

Increase the allocated storage on the target RDS instance to improve performance

Answer

Deploy the target RDS instance as a Single-AZ to simplify replication

Answer

Disable Oracle archivelog mode to speed up data transfer

Question 5

A company is migrating a 500 GB Oracle database to Amazon Aurora PostgreSQL. Which THREE steps should be part of the migration plan?

Accepted Answer

Use AWS DMS to perform a full load and ongoing replication from Oracle to Aurora.. AWS DMS supports heterogeneous migrations from Oracle to Aurora PostgreSQL, performing a full load followed by ongoing change data capture (CDC) using Oracle's redo logs to replicate changes with minimal downtime. This makes it the correct service for both the initial data transfer and continuous replication during migration.

Answer

Use AWS Snowball to transfer the database files.

Answer

Set up AWS Direct Connect between on-premises and AWS.

Question 6

A company is deploying a new application that requires a globally distributed database with low latency reads. They choose Amazon DynamoDB global tables. What is a key consideration for this deployment?

Accepted Answer

Each replica can serve reads and writes independently.. Amazon DynamoDB global tables use a multi-master, active-active replication model. This means each replica region can independently serve both reads and writes, with eventual consistency across regions. This design enables low-latency local reads and writes for globally distributed applications, as each region operates autonomously.

Answer

Writes are synchronously replicated to all regions.

Answer

The table class must be DynamoDB Standard-Infrequent Access.

Answer

Global tables support strongly consistent reads from any region.

Question 7

A company is migrating a 1 TB Amazon RDS for Oracle database to Amazon RDS for PostgreSQL. The migration must be completed within a 4-hour maintenance window. The database has a high volume of transactions. Which migration method minimizes risk of data loss?

Accepted Answer

Use AWS DMS with a full load and change data capture (CDC) enabled, with task restart and validation.. AWS DMS with full load and CDC enables continuous replication of ongoing transactions after the initial load, minimizing data loss risk during the migration window. The task restart and validation features ensure resilience against transient failures and data integrity checks, critical for a high-volume transactional database. This approach meets the 4-hour window by allowing the full load to complete within the window while CDC captures any changes that occur during and after the load.

Answer

Use AWS SCT to convert the schema, then use AWS DMS for full load and ongoing replication.

Answer

Set up Oracle log shipping to an EC2 instance, then restore to RDS PostgreSQL.

Answer

Export the Oracle database using Data Pump, import to PostgreSQL using pgloader.

Question 8

A company is migrating a 2 TB PostgreSQL database from on-premises to Amazon RDS for PostgreSQL with minimal downtime. The database is continuously updated. Which migration strategy should be used?

Accepted Answer

Use AWS Database Migration Service (DMS) with ongoing replication from an on-premises source.. AWS DMS supports ongoing replication (change data capture, CDC) from an on-premises PostgreSQL source to Amazon RDS for PostgreSQL, enabling minimal downtime migration. The 2 TB size is well within DMS's capabilities, and CDC captures incremental changes after the full load, allowing near-zero downtime cutover.

Answer

Use AWS Schema Conversion Tool (SCT) and AWS Snowball to transfer data.

Answer

Use AWS Database Migration Service with a full load only, then cut over.

Answer

Use pg_dump and pg_restore during a maintenance window.

Question 9

Which TWO actions can be taken to monitor the health of an Amazon DynamoDB table? (Choose 2.)

Accepted Answer

Enable Amazon CloudWatch metrics for the table. Enabling CloudWatch metrics for a DynamoDB table provides key health indicators such as read/write capacity utilization, throttled requests, and latency. Option E is correct because setting up CloudWatch alarms on ThrottledRequests allows you to proactively detect and respond to throttling events, which directly impacts table health. Option A is incorrect because AWS Trusted Advisor checks overall account limits but does not provide real-time health monitoring of a specific table. Option C is incorrect because DynamoDB Streams capture item-level changes for event-driven processing, not for monitoring the table's operational health. Option D is incorrect because DAX is an in-memory cache that improves read performance, not a monitoring tool.

Answer

Use AWS Trusted Advisor to check table limits

Answer

Enable DynamoDB Streams and process events with AWS Lambda

Answer

Use DynamoDB Accelerator (DAX) to improve response times

Question 10

Refer to the exhibit. A DBA is checking the backup configuration of an RDS MySQL instance. The current time is 2023-03-15T06:00:00Z. What is the most recent point to which the database can be restored?

Accepted Answer

2023-03-15T04:30:00Z. The latest restorable time is 2023-03-15T04:30:00Z, which is within the backup window. Option A is incorrect because 2023-03-15T03:00:00Z is earlier than the latest restorable time, so it is not the most recent point. Option B is incorrect because 2023-03-15T05:30:00Z is later than the latest restorable time, so it is not within the backup window. Option D is incorrect because although the backup window ends at 06:00, the latest restorable time is 04:30, not 06:00.

Answer

2023-03-15T03:00:00Z

Answer

2023-03-15T05:30:00Z

Answer

2023-03-15T06:00:00Z

Question 11

A company is migrating a PostgreSQL database to Amazon Aurora PostgreSQL. The database has a large table that is frequently accessed. The team wants to minimize downtime during the migration. Which TWO strategies should be used together?

Accepted Answer

Use AWS DMS to create a target Aurora DB cluster and replicate data.. AWS DMS can perform a full load of the source PostgreSQL database to Aurora and then set up ongoing change data capture (CDC) replication to apply incremental changes, minimizing downtime by allowing the source to remain operational until cutover. Option A is correct because DMS can create and manage the target Aurora cluster as part of the replication task, while option D is correct because the combination of full load plus ongoing replication is the standard approach for near-zero downtime migrations.

Answer

Take a manual snapshot of the source database and restore it to Aurora.

Answer

Use AWS Schema Conversion Tool (AWS SCT) to convert the schema.

Answer

Configure Aurora as a read replica of the PostgreSQL instance.

Question 12

A company is migrating an on-premises PostgreSQL database to Amazon RDS for PostgreSQL. The database is 2 TB and the migration must have minimal downtime. Which TWO AWS services should be used together to accomplish this?

Accepted Answer

AWS Schema Conversion Tool (AWS SCT). AWS Schema Conversion Tool (AWS SCT) is used to convert the source PostgreSQL schema and objects to be compatible with Amazon RDS for PostgreSQL, handling any heterogenous elements. AWS Database Migration Service (AWS DMS) then performs the continuous data replication from the on-premises database to RDS, enabling minimal downtime by keeping the target in sync until a cutover.

Answer

AWS CloudFormation

Answer

AWS DataSync

Answer

AWS CloudEndure Migration

Question 13

A company is using Amazon Redshift for data warehousing. They notice that query performance has degraded over time. The database administrator checks the system tables and finds that there is significant skew in data distribution across slices. What action should be taken to improve query performance?

Accepted Answer

Recreate the table with a different distribution style, such as KEY distribution on a column with high cardinality.. Data skew causes some slices to have more data, leading to slower queries. Recreating the table with a different distribution style, such as KEY distribution on a column with high cardinality, can distribute data more evenly across slices. Option B is incorrect because adding more nodes does not automatically redistribute existing data; the skewed distribution persists. Option C is incorrect because running VACUUM reclaims space and updates statistics but does not address data skew. Option D is incorrect because modifying sort keys improves query performance by optimizing data ordering but does not fix uneven data distribution across slices.

Answer

Increase the number of nodes in the cluster.

Answer

Run the VACUUM command to reclaim space and update statistics.

Answer

Modify the sort keys to better match the query patterns.

Question 14

A company uses Amazon DynamoDB to store session data for a web application. The table has a partition key of 'SessionId'. The company wants to automatically expire sessions after 1 hour. Which feature should be used?

Accepted Answer

DynamoDB Time to Live (TTL). DynamoDB Time to Live (TTL) is the correct choice because it allows you to define a per-item timestamp attribute (e.g., 'expireAt') that automatically deletes items after a specified duration—in this case, 1 hour. TTL operates at no additional cost, requires no custom code, and handles expiration asynchronously in the background, making it ideal for session data management.

Answer

DynamoDB Global Tables

Answer

AWS Lambda function that scans the table every hour and deletes old items.

Answer

DynamoDB Streams

Question 15

A company is running Amazon Redshift for data warehousing. The data warehouse is used for complex analytical queries. Recently, query performance has degraded due to data skew. Which steps should be taken to address this issue?

Accepted Answer

Re-evaluate the distribution style of the tables.. Data skew in Amazon Redshift occurs when data is unevenly distributed across slices, causing some nodes to process more data than others and degrading query performance. Re-evaluating the distribution style (e.g., switching from AUTO or EVEN to KEY on a column with high cardinality and even distribution, or using ALL for small dimension tables) redistributes the data evenly, mitigating skew and improving parallel query execution.

Answer

Apply sort keys on the skewed columns.

Answer

Apply compression on the skewed columns.

Answer

Increase the number of nodes in the cluster.