DBS-C01 Practice Exam 55 — 20 Questions

Question 1

A development team is building a serverless application that uses Amazon DynamoDB. The team needs to ensure that only the application's Lambda function can read and write data to a specific DynamoDB table. The Lambda function uses an IAM role. How should the team configure access?

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

Accepted Answer

Create an IAM role for the Lambda function with DynamoDB access, and configure a resource-based policy on the DynamoDB table that allows only that role.. DynamoDB supports resource-based policies (also known as table policies) that allow you to specify which IAM roles or users can access the table. By attaching such a policy that grants access only to the Lambda function's execution role, you ensure that only that function can read/write to the table. Option A is incorrect because using a VPC endpoint does not inherently control access to the table; it only controls network traffic. Option B is incorrect because KMS encryption protects data at rest but does not authorize access. Option D is incomplete because while an IAM role with a DynamoDB access policy is necessary, without a resource-based policy on the table that restricts access to that role, other principals with DynamoDB permissions could still access the table.

Answer

Place the DynamoDB table and Lambda function in the same VPC and use a VPC endpoint to control access.

Answer

Encrypt the DynamoDB table with an AWS KMS key and grant the Lambda function decryption permissions.

Answer

Create an IAM role for the Lambda function with a policy that allows DynamoDB access, and attach the role to the function.

Question 2

A company is designing a database for a real-time bidding system that requires sub-millisecond read and write latency for ad impressions. The workload is heavily write-intensive with occasional reads by campaign IDs. Which AWS database service is most suitable?

Accepted Answer

Amazon DynamoDB with DAX. Amazon DynamoDB with DAX is the most suitable choice because DynamoDB provides single-digit millisecond latency for read and write operations at any scale, and DAX (DynamoDB Accelerator) is an in-memory cache that reduces read latency to microseconds for frequently accessed items. This combination meets the sub-millisecond read and write latency requirements for a heavily write-intensive real-time bidding system, while supporting occasional reads by campaign IDs via efficient query patterns.

Answer

Amazon ElastiCache for Redis

Answer

Amazon DocumentDB

Answer

Amazon Aurora MySQL

Question 3

A company is migrating an on-premises Oracle database to Amazon RDS for Oracle. The security team requires that all data be encrypted at rest using a key stored in AWS CloudHSM. What must be done to meet this requirement?

Accepted Answer

Use Oracle Transparent Data Encryption (TDE) with CloudHSM as the key store.. Use Oracle Transparent Data Encryption (TDE) with CloudHSM as the key store. RDS for Oracle supports TDE, which allows encryption at rest using keys stored in CloudHSM. Option A is incorrect because RDS encryption at rest uses AWS KMS, and while KMS can use a CloudHSM key as a custom key store, the question specifies the key must be stored in CloudHSM directly, which is achieved via TDE integration. Option B is incorrect because RDS does not support custom file system encryption; encryption at rest is managed at the database or instance level. Option C is incorrect because SSL/TLS provides encryption in transit, not at rest.

Answer

Enable RDS encryption at rest using a KMS key backed by CloudHSM.

Answer

Create an encrypted file system on the RDS instance using CloudHSM.

Answer

Configure SSL/TLS for the database connection.

Question 4

A company needs to rotate the master user password for an Amazon RDS for MySQL DB instance. What is the recommended way to do this without downtime?

Accepted Answer

Use the AWS Management Console, CLI, or API to modify the DB instance with a new master password.. Using the AWS Management Console, CLI, or API to modify the DB instance with a new master password updates the password without any downtime or reboot. Option A is incorrect because modifying the DB instance and setting a new password does not cause a reboot; password changes take effect immediately. Option B is incorrect because updating the DB parameter group does not change the master password. Option D is incorrect because deleting and relaunching the instance is unnecessary and would cause downtime.

Answer

Modify the DB instance and set a new password, which will cause a reboot for the change to take effect.

Answer

Update the DB parameter group with the new password.

Answer

Delete the DB instance and launch a new one with the new password.

Question 5

A company runs a critical OLTP workload on Amazon RDS for PostgreSQL. The database size is 2 TB and growing. To reduce storage costs, the company wants to archive old data that is rarely accessed. Which approach is most cost-effective and minimally impacts performance?

Accepted Answer

Implement table partitioning and use S3 as an external table for old partitions.. It uses PostgreSQL table partitioning (e.g., range partitioning by date) combined with the `postgres_fdw` or `pg_parquet` extension to treat old partitions as foreign tables stored in Amazon S3. This keeps the hot data in RDS for fast OLTP access while offloading cold data to low-cost S3 storage, minimizing performance impact and reducing storage costs without requiring a full migration or schema redesign.

Answer

Move the database to Amazon Aurora PostgreSQL with storage auto-scaling.

Answer

Migrate the entire database to Amazon DynamoDB.

Answer

Delete old rows and run VACUUM FULL to reclaim space.

Question 6

A company runs an online transaction processing (OLTP) workload on Amazon RDS for PostgreSQL. The database has grown to 2 TB and the company needs to run complex analytical queries that join multiple large tables. These analytical queries are slowing down the OLTP operations. What is the MOST cost-effective solution to separate the workloads?

Accepted Answer

Create an RDS for PostgreSQL read replica and route analytical queries to it.. Creating an RDS for PostgreSQL read replica is the most cost-effective solution because it offloads analytical queries to a separate read-only instance without requiring a full database migration. The read replica uses PostgreSQL's native streaming replication to maintain near-real-time data consistency, allowing complex joins on large tables without competing for the primary instance's I/O and CPU resources. This approach minimizes operational overhead and cost compared to migrating to a separate analytics platform like Redshift.

Answer

Use Amazon ElastiCache for caching analytical query results.

Answer

Migrate the analytical queries to Amazon Redshift.

Answer

Migrate the OLTP workload to Amazon DynamoDB.

Question 7

Which TWO of the following are valid considerations when designing a database for an e-commerce application with high read traffic and low write latency requirements?

Accepted Answer

Use Amazon DynamoDB Accelerator (DAX) to improve read performance.. Amazon DynamoDB Accelerator (DAX) is a fully managed, in-memory cache for DynamoDB that delivers up to 10x read performance improvement by reducing response times from milliseconds to microseconds. For an e-commerce application with high read traffic and low write latency requirements, DAX offloads read-heavy workloads from the DynamoDB table, ensuring consistent low-latency reads without impacting write throughput.

Answer

Store session data in Amazon S3 for fast access.

Answer

Use Amazon Redshift to serve read traffic directly.

Answer

Deploy Amazon RDS for MySQL with Multi-AZ for read scaling.

Question 8

A company is deploying a new application that requires low-latency reads from a relational database across multiple AWS Regions. The application is read-heavy and can tolerate eventual consistency. Which deployment option meets these requirements?

Accepted Answer

Deploy Amazon Aurora Global Database with a primary Region and read replicas in secondary Regions.. Amazon Aurora Global Database is designed for low-latency global reads and disaster recovery, allowing up to five secondary Regions with dedicated read replicas that replicate data with a typical latency of under one second. This meets the requirement for low-latency reads across multiple Regions while tolerating eventual consistency, as reads from secondary Regions are eventually consistent with the primary.

Answer

Deploy Amazon RDS for PostgreSQL with Multi-AZ and read replicas in the same Region.

Answer

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

Answer

Deploy Amazon DynamoDB Global Tables in multiple Regions.

Question 9

A company uses Amazon DynamoDB to store user session data. The security team requires that all data be encrypted at rest using a customer-managed AWS KMS key. The DynamoDB table is already configured with AWS managed KMS encryption. How can the company meet the encryption requirement without recreating the table?

Accepted Answer

Use the UpdateTable API to specify the new KMS key in the SSESpecification parameter.. DynamoDB supports updating the server-side encryption settings on an existing table using the UpdateTable API with the SSESpecification parameter. This allows you to change from an AWS managed KMS key to a customer managed KMS key without recreating the table or causing downtime. Option A is incorrect because DynamoDB Streams are used for change data capture and cannot modify encryption settings. Option B is incorrect because exporting to S3 and importing into a new table is unnecessary and introduces additional complexity and potential downtime when an in-place update is available. Option D is incorrect because deleting and recreating the table would result in data loss and downtime, and is not required as the UpdateTable API can change encryption directly.

Answer

Enable DynamoDB Streams and use a Lambda function to copy data to a new table with the desired encryption.

Answer

Export the table to Amazon S3 using the on-demand backup feature, then import it into a new table encrypted with the desired KMS key.

Answer

Delete the table and recreate it with the new KMS key.

Question 10

A company uses Amazon DynamoDB with a global secondary index (GSI). The security team requires that only specific IAM users can query the GSI. Which THREE conditions must be met to restrict access to the GSI?

Accepted Answer

The user must have permission to query the base table as well.. The correct answers are C, D, and E. To restrict access to a GSI, you must ensure the user has permission to query the base table (C), allow the dynamodb:Query action on the index (D), and specify the index ARN in the Resource element (E). Option A is incorrect because the dynamodb:IndexName condition key is not used for IAM authorization; access to a GSI is controlled via the resource ARN, not a condition key. Option B is incorrect because the dynamodb:Attributes condition key restricts which attributes are returned, not access to the GSI itself.

Answer

The policy must include a condition 'dynamodb:IndexName' with the index name.

Answer

The policy must include a condition key 'dynamodb:Attributes' to restrict which attributes are returned.

Question 11

A company is planning to migrate a 2 TB Oracle database to Amazon Aurora PostgreSQL. The database contains large objects (LOBs) and uses stored procedures. Which TWO steps should the company take as part of the migration? (Choose two.)

Accepted Answer

Use AWS Schema Conversion Tool (SCT) to convert the Oracle schema and stored procedures to PostgreSQL-compatible format.. The AWS Schema Conversion Tool (SCT) is specifically designed to convert Oracle schema objects, including stored procedures, to PostgreSQL-compatible format. Since the migration involves stored procedures, SCT is necessary to handle the syntax and logic differences between Oracle PL/SQL and PostgreSQL PL/pgSQL, ensuring the target database schema is ready for migration.

Answer

Set up AWS DMS ongoing replication to keep the target in sync after migration.

Answer

Use AWS DMS native Oracle to PostgreSQL endpoint to migrate data without schema conversion.

Answer

Enable RDS Proxy to reduce connection overhead during migration.

Question 12

A company uses Amazon RDS for MySQL with Multi-AZ deployment. The database experiences intermittent write latency spikes. CloudWatch shows elevated 'WriteLatency' and 'WriteIOPS' but normal 'CPUUtilization'. Which is the MOST likely cause?

Accepted Answer

The instance is exceeding the provisioned IOPS burst balance. Intermittent write latency spikes with high WriteIOPS and normal CPU utilization indicate storage performance issues. For RDS MySQL using gp2 or io1 storage, exceeding the provisioned IOPS burst balance (for gp2) or provisioned IOPS (for io1) causes throttling and increased latency. Option A is incorrect because parameter group changes require a reboot and affect all operations, not just intermittent writes. Option C is incorrect because read replicas are read-only and cannot be used for write operations. Option D is incorrect because Multi-AZ replication uses synchronous standby replication, which typically does not cause noticeable write latency spikes; latency from replication is usually minimal.

Answer

A parameter group change was applied without rebooting

Answer

A read replica is being used for write operations

Answer

Multi-AZ replication is causing synchronous writes to the standby

Question 13

A company uses Amazon RDS for Oracle with a custom application that generates complex hierarchical queries using CONNECT BY. They want to migrate to Amazon Aurora to reduce licensing costs. Which migration strategy requires the fewest application changes?

Accepted Answer

Migrate to Amazon Aurora PostgreSQL and rewrite hierarchical queries to use recursive CTEs.. Aurora PostgreSQL supports recursive Common Table Expressions (CTEs) via the WITH RECURSIVE clause, which can be used to rewrite Oracle's CONNECT BY hierarchical queries with minimal application changes. This approach avoids the licensing costs of Oracle while preserving the hierarchical query logic, requiring only a syntax rewrite rather than a complete redesign. Aurora MySQL does not support CONNECT BY or recursive CTEs, making PostgreSQL the only Aurora engine that can handle this workload without significant application restructuring.

Answer

Use AWS Database Migration Service (DMS) to migrate directly to Aurora with no application changes.

Answer

Migrate to Amazon Aurora MySQL and use its hierarchical query features.

Answer

Migrate to Amazon RDS for SQL Server and use its recursive CTEs.

Question 14

A database administrator is troubleshooting a slow-performing query on an Amazon RDS for MySQL instance. The slow query log shows the above entry. Based on the exhibit, which index would most improve the query performance?

Accepted Answer

Composite index on (`status`, `created_at`).. The query filters on `status` and then sorts or filters on `created_at`. A composite index on (`status`, `created_at`) allows MySQL to use the index for both the equality condition on `status` and the range or sort on `created_at`, avoiding a filesort and reducing row scans. This is the most efficient index for this query pattern.

Answer

Index on `created_at` only.

Answer

Index on `status` only.

Answer

Full-text index on `status` and `created_at`.

Question 15

A company uses Amazon DynamoDB with DAX and wants to implement fine-grained access control using IAM. Which THREE conditions can be used in an IAM policy to restrict access to specific items based on the primary key?

Accepted Answer

dynamodb:Attributes. Options A, D, and E are correct. DynamoDB supports fine-grained access control using IAM conditions: dynamodb:LeadingKeys restricts access based on partition key, dynamodb:Attributes controls access to specific attributes, and dynamodb:Select restricts the use of Select parameters. Option B (dynamodb:ReturnValues) is a write operation parameter, not a condition for access control. Option C (dynamodb:TableName) identifies the table, not specific items.

Answer

dynamodb:ReturnValues

Answer

dynamodb:TableName

Question 16

A social media company runs a large Amazon DynamoDB table (Users) with 10 TB of data. The table uses on-demand capacity. Recently, the application started experiencing occasional ProvisionedThroughputExceeded exceptions during read-heavy periods. The table's read metrics show that consumed read capacity is consistently below 50% of provisioned capacity. The application uses eventually consistent reads. The table has a global secondary index (GSI) on the 'status' attribute. The GSI's read capacity consumption is often at 100% of its provisioned capacity. What is the most likely cause of the throttling?

Accepted Answer

The GSI is throttling because its read capacity is not set to on-demand, or the GSI's partition key is causing hot partitions.. The GSI has its own read capacity settings. If the GSI is throttled, reads on the base table that require the GSI may also be throttled. Option C is correct because the GSI is likely using provisioned capacity, not on-demand, and its read capacity is often at 100%, causing throttling. Option A is incorrect because on-demand capacity mode for the base table is not the issue; the issue is the GSI. Option B is incorrect because the base table's read capacity is not the bottleneck (consumed read capacity is below 50%). Option D is incorrect because using strongly consistent reads would increase read consumption, not reduce throttling.

Answer

The on-demand capacity mode is not suitable for this workload; switch to provisioned with auto scaling.

Answer

The base table's read capacity is insufficient despite on-demand mode.

Answer

The application should use strongly consistent reads to reduce throttling.

Question 17

A gaming company uses Amazon Aurora PostgreSQL for its leaderboard data. The database has a writer instance and two reader instances. The application frequently queries the leaderboard to display top players. The queries involve sorting and aggregation on a large table with millions of rows. Recently, the queries started timing out during peak hours. The database administrator analyzed the workload and found that the reader instances are underutilized, while the writer instance has high CPU due to write operations. The administrator wants to offload the read-heavy leaderboard queries to the readers without modifying the application code. What should the administrator do?

Accepted Answer

Configure the application to use the Aurora reader endpoint for read-only queries.. The Amazon Aurora reader endpoint automatically distributes read-only connections across all available reader instances. Since the reader instances are underutilized, using the reader endpoint offloads the read-heavy leaderboard queries from the writer instance without any application code modifications. Option B is incorrect because upgrading the writer instance does not offload read queries and does not utilize the underutilized readers. Option C is incorrect because the existing readers are underutilized; adding more readers would not solve the problem of directing queries to them. Option D is incorrect because creating a separate read-only Aurora cluster is unnecessary and more complex than using the existing reader endpoint.

Answer

Upgrade the writer instance to a larger instance class to handle both read and write operations.

Answer

Create additional reader instances to distribute the read load.

Answer

Implement a read-only Aurora cluster and point read queries to it.

Question 18

A company is running a MongoDB-compatible database on Amazon DocumentDB. The application performs frequent updates to a small subset of fields in documents. The company notices that write latency is high. What should the database specialist recommend to reduce write latency?

Accepted Answer

Review and remove unnecessary indexes on the collection.. Unnecessary indexes impose a write penalty on every insert, update, and delete operation. In Amazon DocumentDB, each write must update all indexes on the collection, so removing unused indexes reduces the per-document write overhead and directly lowers write latency for frequent updates to a small subset of fields.

Answer

Increase the instance size of the DocumentDB cluster.

Answer

Enable multi-master writes to distribute write load.

Answer

Change the storage type from standard to provisioned IOPS.

Question 19

A development team is using Amazon DynamoDB with on-demand capacity mode for a new application. During initial testing, they notice that write requests are occasionally throttled during traffic bursts. They have enabled DynamoDB Accelerator (DAX) for read-heavy operations. What is the best recommendation to eliminate write throttling?

Accepted Answer

Review the table's partition key design to avoid hot keys.. Write throttling in DynamoDB on-demand mode indicates a hot partition, often due to uneven partition key distribution. Reviewing and improving partition key design can eliminate hot keys and distribute write traffic evenly, preventing throttling. Option A is incorrect: while adaptive capacity helps, it does not fully resolve throttling from skewed access patterns. Option B is incorrect: provisioned capacity with Auto Scaling adds complexity but does not address hot partitions; on-demand already scales automatically. Option C is incorrect: DAX is a read cache and does not affect write operations; increasing DAX node size only improves read performance.

Answer

Enable DynamoDB adaptive capacity to automatically adjust partition throughput.

Answer

Switch to provisioned capacity mode with Auto Scaling.

Answer

Increase the DAX cluster node size to handle more write traffic.

Question 20

A company is migrating a 2 TB Oracle database to Amazon RDS for Oracle. The database has a large number of stored procedures, triggers, and functions. The company wants to minimize changes to the application code. Which AWS service should be used to assess and convert the database schema?

Accepted Answer

AWS Schema Conversion Tool (SCT). AWS Schema Conversion Tool (SCT) is designed specifically to convert database schemas from one engine to another, including Oracle to Amazon RDS for Oracle. It assesses the source schema, identifies incompatibilities, and automatically converts stored procedures, triggers, and functions to minimize application code changes. SCT also provides action items for any manual remediation needed, ensuring a smooth migration with minimal code rewrites.

Answer

AWS Database Migration Service (DMS)

Answer

AWS CloudEndure Migration

Answer

AWS CodeCommit