DBS-C01 Practice Test 37 — 15 Questions

Question 1

A company is migrating a MySQL database to Amazon Aurora MySQL. The migration must be completed with minimal downtime. Which TWO methods can achieve this? (Choose two.)

Accepted Answer

Create an Aurora MySQL read replica from the external MySQL instance using binlog replication. You can set up an external MySQL instance as a replication source for an Amazon Aurora MySQL read replica using binary log (binlog) replication. This allows the Aurora cluster to stay synchronized with the source database with minimal downtime, as you only need to stop writes on the source and promote the Aurora replica when ready. Option D is correct because AWS Database Migration Service (AWS DMS) supports ongoing replication using change data capture (CDC) to keep the target Aurora database continuously synchronized with the source MySQL database, enabling a migration with minimal downtime. Options B, C, and E are incorrect: taking a physical backup and restoring (B) or creating an Aurora clone from the source (C) would require downtime; enabling binlog replication alone (E) is not sufficient—it must be used with a replication setup or a service like DMS.

Answer

Take a physical backup of the source database and restore to Aurora

Answer

Create an Aurora clone from the source database

Answer

Enable binlog replication on the source MySQL instance

Question 2

A financial services company is using Amazon Aurora MySQL as its primary database. The database has a table 'transactions' that receives high inserts during business hours. The table is partitioned by date. Recently, the application team noticed an increase in lock wait timeouts. The database specialist reviewed the InnoDB status and found that there are frequent gap locks on the 'transaction_date' column. The isolation level is REPEATABLE READ. What should the specialist do to reduce lock waits while maintaining data consistency?

Accepted Answer

Change the transaction isolation level to READ COMMITTED.. In REPEATABLE READ isolation level, InnoDB uses gap locks on non-unique indexes to prevent phantom reads, which can cause lock wait timeouts. Changing to READ COMMITTED eliminates gap locks for non-unique indexes because it only uses row-level locks (no gap locks). This reduces lock contention. Option A is incorrect: adding an index on transaction_date does not eliminate gap locks if the index is non-unique; gap locks still occur. Option B is incorrect: increasing innodb_lock_wait_timeout only increases the time a transaction waits for a lock, it does not prevent the lock from happening. Option C is incorrect: modifying the partition key does not affect the locking mechanism at the row level.

Answer

Add a secondary index on transaction_date.

Answer

Increase the innodb_lock_wait_timeout parameter.

Answer

Modify the partitioning key to use a hash-based partition.

Question 3

A company is migrating a 2 TB Oracle database from on-premises to Amazon RDS for Oracle using AWS DMS. The migration completes successfully, but the new RDS instance shows higher CPU utilization than the on-premises database for the same workload. Which action is MOST likely to reduce CPU utilization on RDS?

Accepted Answer

Increase the allocated storage to improve IOPS. Increasing allocated storage on Amazon RDS for Oracle directly improves the provisioned IOPS (if using Provisioned IOPS) or baseline IOPS (for gp2/gp3). Higher IOPS reduces I/O wait time, which is a common cause of high CPU utilization when the database is I/O-bound. Query optimization or instance resizing may also help, but increasing storage is a simple, low-risk action that often alleviates I/O-related CPU pressure. Option B is incorrect because Oracle Multitenant (CDB/PDB) architecture adds container management overhead and is not designed to reduce CPU utilization; also, converting an existing non-CDB RDS instance to CDB is not supported.

Answer

Disable automated backups to free resources

Answer

Enable Oracle Multitenant architecture

Answer

Change the RDS instance to a burstable class

Question 4

A startup is building a real-time leaderboard for a gaming application. The data is highly dynamic with frequent updates and requires single-digit millisecond latency. Which database is most suitable?

Accepted Answer

Amazon DynamoDB. Amazon DynamoDB is the most suitable choice because it is a fully managed NoSQL key-value and document database that delivers single-digit millisecond latency at any scale, making it ideal for real-time leaderboards with high-frequency updates. Its DAX (DynamoDB Accelerator) caching layer can further reduce read latency to microseconds, while its auto-scaling and on-demand capacity modes handle the highly dynamic workload without downtime.

Answer

Amazon Neptune

Answer

Amazon Redshift

Answer

Amazon RDS for PostgreSQL

Question 5

Refer to the exhibit. An IAM policy allows creation of a DMS replication task only if the source database engine is Oracle. A user attempts to create a replication task with a MySQL source. What will happen?

Accepted Answer

The action will be denied because the condition does not match.. The IAM policy includes a condition that requires the source engine to be Oracle. When the user attempts to create a DMS replication task with a MySQL source, the condition fails, and IAM denies the action by default. The explicit deny is not needed; IAM uses an implicit deny when no policy statement allows the action under the given conditions.

Answer

The action will fail with an error because the policy is malformed.

Answer

The action will succeed but the task will fail later.

Answer

The action will be allowed because the resource is '*'.

Question 6

A company is designing a multi-region active-active application that requires low-latency reads and writes across regions. The database must support conflict resolution. Which database should be used?

Accepted Answer

Amazon DynamoDB Global Tables. Amazon DynamoDB Global Tables is the correct choice because it provides a fully managed, multi-region, multi-active database that replicates data across regions with eventual consistency, supporting low-latency reads and writes. It includes built-in conflict resolution using a last-writer-wins (LWW) mechanism based on timestamps, which meets the requirement for conflict resolution in an active-active architecture.

Answer

Amazon RDS Multi-AZ

Answer

Amazon Redshift

Answer

Amazon Aurora Global Database

Question 7

Which TWO methods can be used to encrypt an existing unencrypted Amazon RDS for Oracle DB instance? (Choose 2.)

Accepted Answer

Create a snapshot of the DB instance, copy the snapshot with encryption enabled, and restore the DB instance from the encrypted snapshot.. You can encrypt an existing unencrypted RDS for Oracle DB instance by taking a snapshot, copying it with encryption enabled, and then restoring the instance from the encrypted snapshot. This process creates a new encrypted DB instance from the snapshot copy, effectively encrypting the data at rest using AWS KMS. Option D is correct because AWS DMS can migrate data from an unencrypted source DB instance to a new target DB instance that has encryption enabled, allowing you to move the data while applying encryption during the migration process.

Answer

Use the AWS Management Console to toggle encryption on the DB instance.

Answer

Modify the DB instance and enable encryption in the configuration.

Answer

Create a read replica with encryption enabled.

Question 8

Which THREE design patterns can improve the performance of a write-heavy application using Amazon DynamoDB?

Accepted Answer

Write sharding by using a composite key with a random suffix to distribute writes across partitions.. Write sharding with a random suffix on the partition key distributes writes evenly across multiple partitions, preventing hot partitions. This pattern avoids throttling by ensuring no single partition exceeds its write capacity limit, which is critical for write-heavy workloads in DynamoDB.

Answer

Create local secondary indexes (LSIs) for all query patterns.

Answer

Increase provisioned write capacity units (WCUs) to the maximum allowed.

Question 9

A company is running a MongoDB-compatible workload on Amazon DocumentDB. They are experiencing high write latency during peak hours. The current cluster has one instance (db.r5.large) with 100 GB storage. Which change is most likely to improve write performance?

Accepted Answer

Increase the instance size to db.r5.xlarge. Increasing the instance size to db.r5.xlarge provides more CPU and memory resources, which directly improves the cluster's ability to handle write operations under load. In Amazon DocumentDB, write performance is primarily bound by the instance's compute capacity (vCPUs and memory) for processing write requests and managing the storage engine's buffer cache. A larger instance reduces contention and allows more concurrent writes to be processed efficiently.

Answer

Increase storage to 500 GB

Answer

Enable Multi-AZ deployment

Answer

Add a read replica in a different Availability Zone

Question 10

An IAM policy is shown in the exhibit. What is the effect of this policy when a user tries to create an unencrypted RDS DB instance?

Accepted Answer

The user is denied from creating the unencrypted instance because of the Deny statement.. The IAM policy includes an Allow statement for 'rds:CreateDBInstance' and a Deny statement with a condition 'rds:StorageEncrypted=false'. When the user attempts to create an unencrypted RDS instance, the Deny statement explicitly denies the action because the condition is met (encryption is not enabled). Explicit Deny always overrides any Allow, so the user is denied. Option B is incorrect because the Deny statement is valid under IAM policy evaluation logic. Option C is incorrect because the Deny is explicit, not implicit, and only applies to unencrypted instances, not all DB instances. Option D is incorrect because the Deny explicitly overrides the Allow for unencrypted instances.

Answer

The user is allowed to create the unencrypted instance because the Deny statement is not valid.

Answer

The user is denied from creating any DB instance because of an implicit deny.

Answer

The user is allowed to create the unencrypted instance because of the Allow statement.

Question 11

A company wants to migrate a 2 TB Amazon RDS for MySQL DB instance to Amazon Aurora MySQL. The migration must have zero downtime and must be reversible for 48 hours. Which strategy meets these requirements?

Accepted Answer

Create an Aurora MySQL Read Replica from the RDS MySQL instance, then promote the replica to a standalone Aurora cluster.. Creating an Aurora MySQL Read Replica from an RDS MySQL instance uses MySQL's native asynchronous replication to keep the Aurora cluster in sync with the source, allowing a near-zero-downtime cutover by promoting the replica. The migration is fully reversible within 48 hours because the original RDS instance remains unchanged and can continue serving traffic if the promotion is rolled back.

Answer

Take a snapshot of the RDS MySQL instance, restore it to Aurora MySQL, and update the DNS.

Answer

Export the database using mysqldump, import into Aurora, and switch DNS.

Answer

Use AWS DMS with ongoing change data capture (CDC) to migrate to Aurora.

Question 12

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 13

A database specialist created the above IAM policy for a user. When the user attempts to delete an item from the Orders table, what happens?

Accepted Answer

The user cannot delete items because the Deny statement takes precedence.. In IAM, an explicit Deny overrides any Allow. Even though there is an Allow statement that grants DeleteItem permission, the explicit Deny for DeleteItem takes precedence, so the user cannot delete items. Option B is incorrect because the presence of a condition is irrelevant; the Deny is unconditional. Option C is incorrect because the Allow is overridden by the Deny. Option D is incorrect because the Deny in this policy explicitly blocks deletion regardless of other policies.

Answer

The user cannot delete items because the policy does not include a condition.

Answer

The user can delete items because the Allow statement grants permission.

Answer

The user can delete items only if they have another policy that allows it.

Question 14

A company is designing a secure strategy for managing Amazon RDS for Oracle encryption keys. They want to use AWS KMS with Customer Master Keys (CMKs) for encryption at rest. Which THREE best practices should they follow?

Accepted Answer

Grant the RDS service principal (rds.amazonaws.com) only the necessary KMS permissions to use the CMK.. Options A, B, and E are correct. Using separate KMS keys for different environments provides isolation (option B), enabling automatic key rotation is a security best practice (option E), and granting least privilege access to KMS keys is fundamental (option A). Option C is incorrect because disabling key rotation is not recommended and can lead to security risks. Option D is incorrect because storing the CMK inside the database is insecure and defeats the purpose of using KMS.

Answer

Disable key rotation to maintain consistent encryption across all snapshots.

Answer

Store the KMS CMK inside the Oracle database for faster encryption.

Question 15

A company runs a global e-commerce platform with a relational database. They need to reduce read latency for users in Europe and Asia. The primary database is in us-west-2. Which solution provides the LOWEST read latency for global users while maintaining data consistency?

Accepted Answer

Use Amazon Aurora Global Database with reader instances in Europe and Asia. Amazon Aurora Global Database is designed for low-latency global reads by replicating data to up to five secondary regions with dedicated reader instances. It uses storage-based replication that typically adds less than one second of lag, ensuring strong consistency while providing local read access for users in Europe and Asia. This architecture directly addresses the requirement for the lowest read latency without compromising data consistency.

Answer

Deploy Amazon ElastiCache clusters in each region and cache database queries

Answer

Migrate to Amazon DynamoDB global tables

Answer

Configure Amazon RDS cross-region read replicas