DBS-C01 Practice Test 21 — 15 Questions

Question 1

A database administrator needs to monitor the number of database connections to an Amazon RDS for PostgreSQL instance. Which Amazon CloudWatch metric should the administrator use?

Accepted Answer

DatabaseConnections. The correct metric is `DatabaseConnections`, which is published by Amazon RDS for PostgreSQL to CloudWatch. It reports the number of client network connections to the database instance, corresponding to the `numbackends` value from the `pg_stat_database` view. This metric directly reflects the current connection count and is the standard way to monitor connection usage for RDS PostgreSQL.

Answer

ActiveConnections

Answer

ConnectionsCount

Answer

DBInstanceIdentifier

Question 2

A developer is migrating a self-managed MongoDB database to Amazon DocumentDB. The database contains 500 GB of data. What is the most efficient method to perform the initial data load?

Accepted Answer

Use mongodump and mongorestore. Mongodump and mongorestore are the native MongoDB tools designed for logical backups and restores, and Amazon DocumentDB is wire-protocol compatible with MongoDB 3.6 and 4.0. This method efficiently exports the 500 GB dataset as BSON files and imports them directly into DocumentDB, preserving indexes and data types without the overhead of file-system-level differences.

Answer

Take a file system snapshot and restore to DocumentDB

Answer

Use AWS DMS with full load

Answer

Use mongodump with --out and then import using mongoimport

Question 3

A company is migrating a 4 TB Oracle database to Amazon Aurora PostgreSQL using AWS DMS. The migration completes successfully but the application experiences high latency on the Aurora cluster. The DMS task used LOB mode 'full LOB mode'. What is the most likely cause of the latency?

Accepted Answer

Full LOB mode caused large LOBs to be stored in the Aurora cluster, leading to increased I/O. Full LOB mode in AWS DMS loads entire LOBs into memory before writing them to the target, which can cause large LOBs to be stored in the Aurora cluster. This increases I/O and storage overhead, leading to high latency on the Aurora cluster, especially if the LOBs are significantly larger than the default chunk size or if the cluster's I/O capacity is exceeded.

Answer

The Aurora cluster was underprovisioned for parallel load

Answer

The DMS task was configured with 'ongoing replication' causing continuous write load

Answer

The DMS task replicated data to a different region, causing network latency

Question 4

A company is running an Amazon Aurora MySQL-compatible edition DB cluster. The application reports that a recent schema change caused a significant increase in the number of deadlocks. Which parameter should the DBA check and possibly adjust to reduce deadlocks?

Accepted Answer

transaction_isolation. Adjusting the transaction isolation level can reduce deadlocks by decreasing the locking overhead. For example, using READ COMMITTED instead of REPEATABLE READ reduces the use of gap locks, which are a common source of deadlocks. Option A, innodb_lock_wait_timeout, determines how long a transaction waits for a lock before timing out; it does not prevent deadlocks but rather handles lock waits. Option B, autocommit, affects when transactions are committed but does not directly impact deadlock occurrence. Option C, max_connections, limits concurrent connections, which can reduce overall contention but is not a direct deadlock reduction parameter.

Answer

innodb_lock_wait_timeout

Answer

autocommit

Answer

max_connections

Question 5

A company is designing a disaster recovery strategy for Amazon DynamoDB. The strategy must have an RPO of 5 minutes and RTO of 1 hour. Which TWO options meet these requirements? (Choose 2.)

Accepted Answer

Point-in-time recovery (PITR). Point-in-time recovery (PITR) enables continuous backups of DynamoDB tables with 1-second granularity over a 35-day window, allowing restoration to any point within that window. This supports an RPO of 5 minutes because you can restore to a specific timestamp within seconds of the failure, and the RTO of 1 hour is achievable as table restoration typically completes within that timeframe for most table sizes.

Answer

On-demand backups

Answer

Cross-Region Replication (CRR) to S3

Answer

Scheduled backups using AWS Backup

Question 6

A company is deploying a globally distributed application that requires a low-latency, highly available database with multi-region write support. The application needs to handle conflicts automatically. Which AWS database solution meets these requirements?

Accepted Answer

Amazon DynamoDB global tables. Amazon DynamoDB global tables provide a fully managed, multi-region, multi-active database solution that automatically replicates data across AWS Regions, supports low-latency reads and writes from any region, and uses conflict resolution based on 'last writer wins' (LWW) with a timestamp vector clock. This meets the requirement for a globally distributed application needing automatic conflict handling without custom code.

Answer

Amazon Aurora Global Database

Answer

Amazon ElastiCache for Redis global datastore

Answer

Amazon RDS Multi-AZ with cross-region read replicas

Question 7

A company is deploying a MySQL database on Amazon RDS and needs to enforce encryption at rest. Which configuration step is required?

Accepted Answer

Select encryption option when creating the RDS instance.. Amazon RDS for MySQL requires encryption at rest to be enabled at instance creation time by selecting the encryption option in the AWS Management Console, CLI, or API. Encryption at rest uses AWS Key Management Service (KMS) to encrypt the underlying storage, automated backups, read replicas, and snapshots. This setting cannot be applied to an existing unencrypted DB instance, so it must be chosen during the initial launch.

Answer

Use a custom DB parameter group with SSL enabled.

Answer

Modify the DB instance to enable encryption after creation.

Answer

Enable SSL/TLS on the RDS instance.

Question 8

A company needs to migrate a 3 TB Amazon RDS for SQL Server database to Amazon RDS for PostgreSQL. The migration must be automated and repeatable with minimal manual intervention. Which combination of services should be used?

Accepted Answer

Use AWS Schema Conversion Tool (SCT) to convert the schema, then use AWS DMS to migrate the data.. AWS Schema Conversion Tool (SCT) handles the schema conversion from SQL Server to PostgreSQL, which is necessary due to incompatible data types, stored procedures, and indexes. AWS Database Migration Service (DMS) then performs the continuous data migration with minimal downtime, supporting both full load and ongoing replication. This combination automates the migration process and makes it repeatable via AWS CloudFormation or DMS task templates.

Answer

Use AWS SCT to convert the schema and export data to PostgreSQL-compatible format, then import.

Answer

Use AWS DMS with native SQL Server CDC to migrate directly to PostgreSQL.

Answer

Use Microsoft Data Migration Assistant to assess and migrate to PostgreSQL.

Question 9

A database specialist is monitoring an Amazon RDS for MySQL instance and notices that the 'CPUUtilization' metric is consistently above 90%. Which TWO actions should the specialist take to investigate the issue? (Select TWO.)

Accepted Answer

Use Performance Insights to identify the queries that are consuming the most CPU.. Performance Insights identifies the queries that are consuming the most CPU, helping to locate the source of high CPU utilization. Option E is correct because Enhanced Monitoring provides OS-level metrics (e.g., CPU, memory, disk I/O) that help investigate the issue. Option A is incorrect because disabling the query cache does not help investigate CPU usage; it may even increase CPU load temporarily. Option C is incorrect because increasing the instance class is a remediation step, not an investigation action. Option D is incorrect because Multi-AZ does not distribute read load to a standby instance; the standby is only for failover, not for load distribution.

Answer

Disable the MySQL query cache to free up CPU.

Answer

Increase the instance class to provide more CPU resources.

Answer

Enable Multi-AZ to distribute the load to a standby instance.

Question 10

Which TWO of the following are methods to control access to an Amazon RDS DB instance? (Select TWO.)

Accepted Answer

VPC security groups. Options A and B are correct. VPC security groups control network access to the RDS instance at the instance level, acting as a virtual firewall. IAM policies can control who can perform administrative actions on the RDS instance via the AWS API, such as creating, modifying, or deleting the instance. Option C is incorrect because CloudWatch alarms monitor performance metrics and trigger actions, but do not control access. Option D is incorrect because database passwords are a form of authentication for users connecting to the database, not a method to control access to the RDS instance itself. Option E is incorrect because S3 bucket policies control access to Amazon S3 resources, not RDS.

Answer

Amazon CloudWatch alarms

Answer

Database passwords

Answer

Amazon S3 bucket policies

Question 11

A company is using Amazon RDS for MySQL with a cross-Region read replica to support disaster recovery. The primary DB instance is in us-west-2, and the read replica is in us-east-1. The read replica is used for reporting and also serves as a failover target. The operations team notices that the read replica lag is consistently above 10 seconds during peak hours. What should the team do to reduce replica lag?

Accepted Answer

Increase the DB instance class of the read replica.. Increasing the DB instance class of the read replica provides more CPU and memory resources, which allows the replica to apply changes from the binary log more quickly. Cross-Region replication lag is often caused by the replica being unable to keep up with the write rate on the primary, so scaling up the replica directly addresses the bottleneck in applying binlog events.

Answer

Enable Multi-AZ on the primary DB instance.

Answer

Increase the backup retention period for the primary DB instance.

Answer

Disable binary logging (binlog) on the primary DB instance.

Question 12

A company is migrating a 5 TB MongoDB database to Amazon DocumentDB. They have a short maintenance window and need to minimize downtime. Which migration strategy should be used?

Accepted Answer

Use AWS DMS to perform a full load and then ongoing replication from the source MongoDB.. AWS DMS supports MongoDB as a source and Amazon DocumentDB as a target, enabling a full load of the 5 TB database followed by ongoing change data capture (CDC) using MongoDB's oplog. This minimizes downtime by keeping the target nearly synchronized during the migration window, allowing a final cutover with minimal interruption.

Answer

Use the MongoDB change streams feature to replicate changes to DocumentDB in real time.

Answer

Set up AWS Direct Connect to the source and use mongorestore directly to DocumentDB.

Answer

Export the data using mongodump, transfer to Amazon S3, and import using mongorestore.

Question 13

A company is migrating a 5 TB Oracle database to Amazon Aurora PostgreSQL. The database has a 4-hour maintenance window weekly. Which migration approach minimizes downtime?

Accepted Answer

Use AWS Database Migration Service (DMS) with change data capture (CDC).. AWS DMS with CDC allows you to perform an initial full load of the 5 TB database and then continuously replicate ongoing changes from the source Oracle database to the target Aurora PostgreSQL. This minimizes downtime because you can keep the source database fully operational during the migration and only perform a brief cutover to switch applications to the new database, well within the 4-hour maintenance window.

Answer

Use Oracle Data Pump to export and pg_restore to import.

Answer

Use AWS Schema Conversion Tool (SCT) to convert schema and then copy data.

Answer

Use AWS DMS full load only and then manually sync.

Question 14

A company wants to run a graph database for a social network application. The data model involves users, posts, comments, and likes, with many-to-many relationships. Which AWS database service is most appropriate?

Accepted Answer

Amazon Neptune. Amazon Neptune is purpose-built for highly connected data, supporting property graph and RDF models with SPARQL and Gremlin/TinkerPop query languages. For a social network with users, posts, comments, and likes forming many-to-many relationships, Neptune efficiently traverses these connections using graph traversal algorithms, avoiding the expensive JOINs or denormalization required by other database types.

Answer

Amazon RDS for PostgreSQL

Answer

Amazon DocumentDB

Answer

Amazon DynamoDB

Question 15

Refer to the exhibit. A developer wants to connect to the database. Which database engine is most likely being used?

Accepted Answer

MySQL. The exhibit shows a connection string using the format `jdbc:mysql://...`, which is the standard JDBC URL prefix for MySQL databases. This indicates the developer is connecting to a MySQL database engine, as Oracle, SQL Server, and PostgreSQL use different JDBC URL prefixes (`jdbc:oracle:thin:`, `jdbc:sqlserver://`, and `jdbc:postgresql://` respectively).

Answer

Oracle

Answer

SQL Server

Answer

PostgreSQL