DBS-C01 Practice Test 45 — 15 Questions

Question 1

A company needs a database for a serverless web application that stores user sessions. The sessions expire after 24 hours. The database must be highly available and require no server management. Which AWS service is most appropriate?

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

Accepted Answer

Amazon DynamoDB with TTL.. Amazon DynamoDB with TTL is the most appropriate choice because it provides a fully managed, serverless, highly available NoSQL database that can automatically expire user sessions after 24 hours using the Time to Live (TTL) feature. DynamoDB's on-demand capacity mode eliminates server management, and its built-in replication across multiple Availability Zones ensures high availability without any manual intervention.

Answer

Amazon ElastiCache for Redis with cluster mode.

Answer

Amazon RDS for PostgreSQL with Multi-AZ.

Answer

Amazon S3 with lifecycle policies.

Question 2

A company is designing a database for a global application that requires active-active replication across two AWS Regions. The database must support multi-master writes with conflict resolution. Which AWS database service should they use?

Accepted Answer

Amazon DynamoDB Global Tables. Amazon DynamoDB Global Tables provides fully managed, multi-Region, multi-master replication, enabling active-active writes across two AWS Regions with built-in conflict resolution using last-writer-wins (based on timestamp). This directly meets the requirement for multi-master writes and conflict resolution without custom code.

Answer

Amazon Aurora Global Database

Answer

Amazon Redshift

Answer

Amazon RDS for MySQL with Multi-AZ

Question 3

Arrange the steps to restore an Amazon RDS for MySQL DB instance to a new instance from a manual snapshot in the correct order.

Accepted Answer

Select the manual snapshot from the list, then configure the new DB instance details, then initiate the restore, then wait for the restore to complete.. Restoring from a manual snapshot involves selecting the snapshot, configuring the new instance, and waiting for completion.

Answer

Configure the new DB instance details, then select the manual snapshot from the list, then initiate the restore, then wait for the restore to complete.

Answer

Select the manual snapshot from the list, then initiate the restore, then configure the new DB instance details, then wait for the restore to complete.

Answer

Wait for the restore to complete, then select the manual snapshot from the list, then configure the new DB instance details, then initiate the restore.

Question 4

A gaming company uses Amazon DynamoDB for player session data. Each session has a partition key of `game_id` and a sort key of `session_id`. The table has a global secondary index (GSI) on `player_id` for leaderboard queries. Recently, the company noticed that write traffic to the GSI is causing throttling on the base table, even though the base table's write capacity is not fully utilized. What is the MOST likely cause?

Accepted Answer

The GSI is not designed with a high-cardinality partition key, causing write hot spots on the GSI.. A global secondary index (GSI) has its own provisioned read and write capacity, separate from the base table. If the GSI's partition key (player_id) has low cardinality (e.g., only a few distinct player_id values), writes to the base table will concentrate on a small number of GSI partitions, causing throttling on the GSI. This throttling on the GSI then back-pressures the base table, resulting in write throttling on the base table even if its own write capacity is underutilized.

Answer

The application is using strongly consistent reads on the GSI, which consumes double the read capacity.

Answer

Point-in-time recovery (PITR) is enabled, consuming extra write capacity.

Answer

The table's auto-scaling settings are not configured correctly for the GSI.

Question 5

A financial services company uses Amazon Redshift for analytics. The workload consists of a mix of short-running queries from dashboards and long-running ETL jobs. The company notices that during peak hours, short queries experience high latency due to queueing behind ETL jobs. How can the company reduce the impact of ETL jobs on dashboard queries?

Accepted Answer

Configure workload management (WLM) queues to separate ETL and dashboard queries, and assign different concurrency levels.. Amazon Redshift's Workload Management (WLM) allows you to create separate queues for different query types, such as ETL jobs and dashboard queries. By assigning different concurrency levels to each queue, you prevent long-running ETL jobs from consuming all available slots and blocking short dashboard queries, thereby reducing latency during peak hours.

Answer

Enable concurrency scaling to handle bursts of queries.

Answer

Enable short query acceleration (SQA) to prioritize queries that run under a certain time threshold.

Answer

Increase the number of nodes in the Redshift cluster.

Question 6

A company is migrating an on-premises MySQL database to Amazon RDS for MySQL. The company wants to minimize application changes. Which endpoint type should the application use after migration?

Accepted Answer

RDS instance endpoint (DNS name). The RDS instance endpoint (DNS name) is the standard connection endpoint for a single RDS DB instance, which is the target of a direct migration from on-premises MySQL to Amazon RDS for MySQL. This endpoint requires no application changes, as the application simply replaces the old on-premises hostname with the RDS instance DNS name, maintaining the same MySQL protocol and connection logic.

Answer

RDS reader endpoint

Answer

RDS cluster endpoint

Answer

RDS console endpoint

Question 7

A team is troubleshooting an Amazon RDS for SQL Server instance that is running out of storage. The instance uses General Purpose SSD (gp2) storage. The team wants to increase storage without downtime. Which action should they take?

Accepted Answer

Modify the DB instance to increase allocated storage.. Amazon RDS supports increasing allocated storage for a DB instance with no downtime by modifying the DB instance's allocated storage setting. This operation is an online change that does not require a reboot and can be applied immediately, allowing the instance to grow its storage volume while remaining available. This is the standard, least-disruptive way to resolve a storage-full condition on RDS.

Answer

Migrate to gp3 storage.

Answer

Add a read replica to offload queries.

Answer

Take a snapshot and restore to a larger instance.

Question 8

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 9

A company is migrating a 2 TB Oracle database from on-premises to Amazon RDS for Oracle. The database has a 4-hour maintenance window and the migration must have minimal downtime. Which AWS service should be used for the migration?

Accepted Answer

Use AWS Database Migration Service (DMS) with ongoing replication from the source database.. AWS DMS with ongoing replication (change data capture) is the correct choice because it allows you to perform a full load of the 2 TB Oracle database and then continuously replicate incremental changes from the source to the target RDS instance. This minimizes downtime by enabling a cutover window of minutes rather than hours, which is critical given the 4-hour maintenance window constraint.

Answer

Use AWS Schema Conversion Tool (SCT) to convert the schema and then perform a full data load.

Answer

Create an RDS Cross-Region Read Replica and promote it to a standalone instance.

Answer

Take a full backup of the on-premises database, upload it to S3, and restore it to RDS.

Question 10

A company needs to store and manage user sessions for a web application. The application runs on multiple EC2 instances, and sessions must be accessible from any instance. The team wants a fully managed, highly available, and low-latency solution. Which AWS service should they use?

Accepted Answer

Amazon ElastiCache for Redis. Amazon ElastiCache for Redis is the correct choice because it provides a fully managed, in-memory data store with sub-millisecond latency, making it ideal for storing user session data that must be accessed from any EC2 instance. Redis supports atomic operations and data structures (e.g., TTL-based key expiration) that are well-suited for session management, and its replication and Multi-AZ failover ensure high availability. This meets the requirement for a fully managed, highly available, and low-latency solution without the overhead of managing a database cluster.

Answer

Amazon RDS for MySQL

Answer

Amazon DynamoDB

Answer

Amazon S3

Question 11

A company needs to store and query JSON documents that vary in structure. The application requires flexible schema, automatic indexing, and the ability to run complex aggregation pipelines. Which AWS database service should be used?

Accepted Answer

Amazon DocumentDB (with MongoDB compatibility). Amazon DocumentDB (with MongoDB compatibility) is the correct choice because it is purpose-built for storing and querying JSON-like documents with flexible schemas, automatically indexes fields, and supports MongoDB's aggregation pipeline for complex data transformations. This aligns directly with the requirements for varying document structures, automatic indexing, and aggregation capabilities.

Answer

Amazon DynamoDB

Answer

Amazon ElastiCache for Redis

Answer

Amazon RDS for PostgreSQL

Question 12

A company is running an Amazon RDS for MySQL DB instance. The database performance has degraded over time. The DBA suspects that the issue is due to a high number of connections that are in a 'sleep' state from a legacy application. What is the MOST effective solution to automatically terminate idle connections?

Accepted Answer

Modify the 'wait_timeout' parameter in the DB parameter group to a lower value.. For Amazon RDS for MySQL, the 'wait_timeout' parameter controls how many seconds the server waits for activity on a non-interactive connection before closing it; lowering it automatically terminates idle 'sleep' connections. Because it is a dynamic parameter in the DB parameter group, you can apply it without rebooting the instance, making it the most effective automated solution for the legacy application's idle connections.

Answer

Increase the 'max_connections' parameter to accommodate more idle connections.

Answer

Enable Amazon RDS Proxy to manage connection pooling and automatically close idle connections.

Answer

Use a script to run 'SHOW PROCESSLIST' and manually kill idle connections.

Question 13

A company is migrating a 2 TB PostgreSQL database from on-premises to Amazon RDS for PostgreSQL. The migration must have minimal downtime and support ongoing replication. Which AWS service should be used for the migration?

Accepted Answer

AWS Database Migration Service (DMS) with change data capture. AWS Database Migration Service (DMS) with change data capture (CDC) is the correct choice because it supports ongoing replication from the source PostgreSQL database to Amazon RDS for PostgreSQL with minimal downtime. DMS performs a full load of the 2 TB database and then continuously applies changes using PostgreSQL's logical replication slots (via the pglogical extension or native WAL-based CDC), ensuring the target remains synchronized during the migration cutover.

Answer

AWS S3 Transfer Acceleration for direct database export

Answer

AWS Data Migration Service with AWS Glue

Answer

AWS Snowball Edge for offline data transfer

Question 14

A company is deploying an Amazon DynamoDB table with server-side encryption using a customer-managed AWS KMS key. The security team requires that the key be automatically rotated every year and that access to the key be logged. Which THREE steps should be taken?

Accepted Answer

Enable automatic key rotation for the KMS key.. Option A is correct because enabling automatic key rotation on a customer-managed KMS key causes AWS KMS to rotate the backing key material once per year (the default rotation period) without changing the key ID or requiring re-encryption of data, satisfying the annual rotation requirement. Option C is correct because AWS KMS API calls such as Encrypt, Decrypt, and GenerateDataKey are recorded by AWS CloudTrail, which is the mechanism that provides the required logging of key access. Option D is correct because a KMS key policy is the primary access control document for a KMS key, and restricting its use to specific IAM roles enforces least-privilege access to the key. Option B is incorrect because AWS CloudHSM is a separate dedicated hardware security module service and is not used to store or rotate KMS keys. Option E is incorrect because client-side encryption moves encryption outside DynamoDB and KMS-managed server-side encryption, which contradicts the stated requirement for DynamoDB server-side encryption with a customer-managed KMS key.

Answer

Use AWS CloudHSM to store the key and manage rotation.

Answer

Configure the DynamoDB table to use client-side encryption.

Question 15

A company is designing a database for a global e-commerce platform. The application requires single-digit millisecond read and write latency for user sessions, and must handle millions of requests per second. The data is key-value in nature. Which TWO AWS services should the company consider? (Choose two.)

Accepted Answer

Amazon DynamoDB. Amazon DynamoDB (A) is correct because it is a fully managed key-value and document NoSQL database that delivers single-digit millisecond latency at any scale and is designed to handle millions of requests per second, matching the key-value data model and performance requirements. Amazon ElastiCache for Redis (B) is also correct because it is an in-memory key-value store that provides sub-millisecond to single-digit millisecond read and write latency and can sustain millions of operations per second, making it ideal for high-throughput user session data. Amazon Neptune (C) is a graph database optimized for highly connected data and relationship queries, not the key-value workload described. Amazon Redshift (D) is a petabyte-scale data warehouse for analytical (OLAP) queries and does not provide the low-latency transactional performance required. Amazon RDS for MySQL (E) is a relational database that generally cannot meet single-digit millisecond latency at millions of requests per second for key-value access patterns without extensive sharding and caching.

Answer

Amazon Neptune

Answer

Amazon Redshift

Answer

Amazon RDS for MySQL