DBS-C01 Practice Exam 68 — 20 Questions

Question 1

A database specialist is troubleshooting an Amazon RDS for SQL Server DB instance that is experiencing slow query performance. The specialist suspects that a specific query is causing high CPU usage. Which AWS tool should be used to identify the top SQL statements by CPU consumption?

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

Accepted Answer

Performance Insights. Performance Insights is a database performance tuning and monitoring feature that helps you quickly assess the load on your database and determine when and where to take action. It provides a top SQL view that shows the SQL statements contributing most to database load, including CPU usage. For SQL Server, it captures this data without requiring additional setup. The other tools lack this query-level detail.

Answer

Amazon CloudWatch Logs

Answer

Amazon RDS Enhanced Monitoring

Answer

AWS CloudTrail

Question 2

A retail company runs an Amazon RDS for PostgreSQL instance for its order management system. The database is read-heavy, and the team wants to add read capacity without changing the application's write connection. The team also wants automatic failover to a standby in a second Availability Zone if the primary fails. Which configuration should the team implement?

Accepted Answer

Enable Multi-AZ with a standby instance and create read replicas, directing read traffic to the read replicas while the primary serves writes.. Multi-AZ with a standby instance delivers automatic failover through synchronous replication to a second Availability Zone, while separate read replicas absorb read-only traffic. Together they meet both the resilience and read-scaling goals without changing the application's writer connection. Snapshot restores and read replicas alone do not provide automatic failover.

Answer

Create a read replica in a second Availability Zone and connect the application exclusively to the read replica endpoint.

Answer

Restore a recent snapshot into a new instance in a different Availability Zone and split the application's connections between both instances.

Answer

Enable a Multi-AZ DB cluster deployment and connect the application to the writer endpoint.

Question 3

A security engineer needs to grant an application running on Amazon EC2 access to an Amazon RDS for PostgreSQL database without storing long-term database passwords on the instance. The application authenticates to AWS using an IAM role attached to the instance profile. Which approach should the engineer use?

Accepted Answer

Enable IAM database authentication on the RDS instance and have the application generate an authentication token using its IAM role.. IAM database authentication replaces the database password with a temporary token derived from the IAM role. The EC2 instance profile provides credentials to sign the token request, and the token is accepted by RDS for PostgreSQL as the password. This removes the need to store or distribute a long-lived database password on the instance.

Answer

Use AWS Systems Manager Parameter Store to hold the password as a SecureString and fetch it at runtime.

Answer

Store the database password in AWS Secrets Manager and retrieve it at application startup using the instance role.

Answer

Create a database user with a strong password and store it in an encrypted Amazon EBS volume attached to the EC2 instance.

Question 4

A database specialist manages an Amazon RDS for SQL Server Multi-AZ instance. The company requires that all backups be encrypted at rest with a customer-managed AWS KMS key. The specialist enabled encryption at rest when creating the instance, but now needs to change the KMS key due to a key rotation policy. What is the correct approach?

Accepted Answer

Take a snapshot, copy the snapshot with the new KMS key, restore to a new instance, and then redirect the application.. Changing the KMS key for an encrypted RDS instance requires creating a snapshot, copying it with the new key, and restoring a new instance. This is because the encryption key is tied to the instance at creation. The new instance will have a new endpoint, necessitating application changes. This method ensures data is encrypted with the desired key.

Answer

Modify the DB instance to use the new KMS key; the change is applied immediately without downtime.

Answer

Use AWS KMS to create a new key and update the key policy to include the RDS service; the instance will automatically re-encrypt.

Answer

Enable automatic key rotation on the existing KMS key; RDS will use the new key material for future backups.

Question 5

A company uses Amazon DynamoDB with a table that has a global secondary index (GSI). The application performs frequent updates to an attribute that is part of the GSI's key schema. The database specialist observes that the GSI's provisioned write capacity is often throttled, even though the base table's write capacity is not. The GSI's write capacity is set to 100 WCU. What is the most likely cause of the throttling?

Accepted Answer

The GSI's write capacity is too low because every update to the GSI key attribute results in a delete and an insert in the GSI, consuming twice the write capacity units.. Updating a GSI key attribute requires DynamoDB to delete the existing index entry and insert a new one. Each operation consumes write capacity units from the GSI. This effectively doubles the write cost for that update. Since the GSI has only 100 WCU, it can become throttled even if the base table has sufficient capacity. Increasing the GSI's write capacity resolves the bottleneck.

Answer

The GSI is throttled because DynamoDB replicates the entire item to the GSI on every update, consuming write capacity proportional to the item size, not just the key attributes.

Answer

The GSI is throttled because the base table's write capacity is consumed by the GSI updates, leaving insufficient capacity for the base table, and the throttling is misattributed to the GSI.

Answer

The GSI's write capacity is not the issue; DynamoDB automatically scales GSI capacity based on the base table's capacity, so the throttling must be due to a hot partition in the base table.

Question 6

A company runs an on-premises Oracle database that must be migrated to Amazon Aurora PostgreSQL within a tight window. The database contains large BLOB columns and several proprietary Oracle data types. The team needs to convert the schema and stored procedures to PostgreSQL-compatible code before the cutover. Which AWS service should be used to perform the schema conversion?

Accepted Answer

AWS Schema Conversion Tool (AWS SCT). AWS Schema Conversion Tool is purpose-built to convert database schemas and procedural code from one engine to another, including Oracle to Aurora PostgreSQL. It handles tables, indexes, views, stored procedures, functions, and data type mappings, and it reports objects requiring manual intervention. AWS DMS then moves the data into the converted schema. DataSync and DMS task settings do not perform schema conversion.

Answer

AWS DataSync with an S3 bucket as the target

Answer

AWS Database Migration Service (AWS DMS) with a full-load plus change data capture task

Answer

AWS Database Migration Service (AWS DMS) with the Schema Conversion action enabled in the task settings

Question 7

A database specialist is responsible for an Amazon RDS for MySQL DB instance. The specialist needs to receive an alert when the average number of database connections exceeds 80% of the maximum allowed for the instance's parameter group over a 5-minute period. Which combination of CloudWatch alarm configuration steps should the specialist use?

Accepted Answer

Create a CloudWatch alarm on the DatabaseConnections metric with a threshold based on the max_connections parameter value, and set the period to 300 seconds with the statistic set to Average.. The DatabaseConnections metric is the correct measure for connection count. To alert at 80% of max_connections, the threshold must be calculated from that parameter, and a 300-second period with Average statistic provides the 5-minute average. The other metrics and static thresholds do not align with the stated requirement.

Answer

Create a CloudWatch alarm on the CPUUtilization metric with a threshold of 80%, and set the period to 300 seconds.

Answer

Create a CloudWatch alarm on the FreeableMemory metric with a threshold of 20% of total memory, and set the period to 300 seconds.

Answer

Create a CloudWatch alarm on the DatabaseConnections metric with a static threshold of 80 connections, regardless of the instance's max_connections parameter.

Question 8

A healthcare analytics company ingests millions of time-stamped patient vitals per hour into Amazon Timestream. Queries must return the latest reading for each patient within 200 milliseconds and retain raw data for 30 days, after which only hourly aggregates are needed for 5 years. Which Timestream configuration should a database specialist choose to meet these requirements MOST cost-effectively?

Accepted Answer

Set the memory store retention to 24 hours, the magnetic store retention to 30 days, and create a scheduled query that writes hourly aggregates into a second Timestream table with 5-year magnetic retention.. Timestream separates a high-performance memory store from a cost-optimized magnetic store, so the correct design keeps only recent raw data in memory, retains raw data in magnetic storage for the required 30 days, and uses a scheduled query to persist hourly aggregates for the 5-year horizon. This matches latency, retention, and cost goals simultaneously.

Answer

Set the memory store retention to 7 days, the magnetic store retention to 30 days, and export hourly aggregates to Amazon S3 with a lifecycle policy for 5 years.

Answer

Set the memory store retention to 30 days and the magnetic store retention to 5 years.

Answer

Set the memory store retention to 24 hours and the magnetic store retention to 5 years.

Question 9

A company is migrating a large on-premises MySQL database to Amazon Aurora MySQL. The migration must be completed with minimal downtime, and the cutover should be quick. The company plans to use AWS DMS with a replication instance. Which TWO actions should be taken to achieve minimal downtime during the cutover? (Choose two.)

Accepted Answer

Enable change data capture (CDC) on the source database before starting the full load.. To achieve minimal downtime with AWS DMS, you must enable CDC to capture ongoing changes and pre-create the target schema to avoid delays during the full load. CDC keeps the target synchronized so that the cutover only requires a brief pause in writes. Pre-creating schema and indexes ensures that the full load runs efficiently and the target is ready for cutover as soon as replication catches up.

Answer

Use full LOB mode to ensure all large objects are migrated quickly.

Answer

Use a single replication instance with maximum allocated storage to handle the full load and CDC.

Answer

Configure the replication instance in a single Availability Zone to reduce latency.

Question 10

A company is designing an Amazon Aurora MySQL cluster for an online transaction processing workload that requires low-latency reads and high availability across three Availability Zones. The team wants to maximize read throughput and minimize failover disruption. Which TWO design choices should the team make? (Choose two.)

Accepted Answer

Deploy Aurora replicas in multiple Availability Zones and route read traffic to the reader endpoint.. Aurora replicas placed across multiple Availability Zones with reader endpoint routing provide read scaling, low-latency reads, and resilience if a replica fails. Aurora Auto Scaling adjusts replica count to match read demand, keeping latency low during spikes and restoring capacity after failures. Concentrating reads on the writer, collapsing to one Availability Zone, or switching to RDS for MySQL read replicas all undermine throughput or availability.

Answer

Use a single writer instance and direct all read traffic to the writer endpoint to simplify routing.

Answer

Configure the Aurora cluster to use a single Availability Zone to reduce replication overhead.

Answer

Replace Aurora replicas with read-only replicas on Amazon RDS for MySQL using binary log replication.

Question 11

A logistics company runs an Amazon RDS for SQL Server Multi-AZ instance. During a nightly batch job, the application experiences a brief outage and the RDS console shows a failover event. After the failover, the application reconnects to the new primary, but the database specialist notices that the old primary's endpoint now resolves to the standby. Which statement correctly describes what happened and how the application should be configured?

Accepted Answer

The CNAME record for the DB instance endpoint was updated to point to the new primary, and the application should continue using the same endpoint name.. In RDS Multi-AZ, the DB instance endpoint is a DNS name that RDS repoints to the new primary after failover. Applications should connect using that endpoint rather than a fixed IP or instance-specific address, so they recover automatically. The observed behavior — the old primary's address now resolving to the standby — is exactly the expected DNS update.

Answer

The failover was triggered by the batch job exceeding the maximum allowed connections, and the application should use RDS Proxy to prevent future failovers.

Answer

The standby became the new primary only after a manual promotion, and the application must update its connection string to the standby's endpoint.

Answer

The application must be reconfigured with the new primary's IP address because the endpoint name is permanently associated with the old primary.

Question 12

A company uses Amazon ElastiCache for Redis to cache session data for a web application. The Redis cluster is in cluster mode disabled with one shard and two replicas. Users are reporting that they are being logged out unexpectedly. A database specialist checks the ElastiCache metrics and notices that the CurrConnections metric is very high and the Evictions metric is increasing. The cache node type is cache.m5.large with 6.38 GiB of memory. What is the MOST likely cause of the session loss?

Accepted Answer

The Redis cluster's maxmemory-policy is set to allkeys-lru, and the cache is evicting session keys due to memory pressure.. The combination of high CurrConnections and increasing Evictions indicates that the Redis instance is running out of memory and evicting keys to make room. With a policy like allkeys-lru, session keys can be evicted, causing users to be logged out. To resolve this, consider increasing the node size, using a more appropriate eviction policy such as volatile-lru if sessions have TTLs, or optimizing memory usage.

Answer

The application is not using Redis correctly; it should store session data in a Redis sorted set instead of strings.

Answer

The Redis cluster is experiencing a failover, causing the primary node to change and session data to be lost.

Answer

The ElastiCache cluster's parameter group has maxmemory-policy set to noeviction, causing writes to fail and sessions to be lost.

Question 13

A company is deploying a new Amazon Aurora MySQL cluster in a single AWS Region. They require that the cluster be able to survive an Availability Zone (AZ) failure with minimal downtime and no data loss. The application uses the cluster endpoint for writes. Which configuration should they choose?

Accepted Answer

Create an Aurora cluster with one writer instance and one reader instance in different AZs.. Aurora stores data across three AZs and supports rapid failover to a reader instance in a different AZ. By provisioning a writer and a reader in separate AZs, the cluster can automatically promote the reader if the writer's AZ fails, with minimal downtime and no data loss. Other options either do not provide AZ redundancy or are not applicable to Aurora.

Answer

Create an Aurora cluster with one writer instance and one reader instance in the same AZ.

Answer

Create an Aurora cluster with a single writer instance and enable Multi-AZ deployment.

Answer

Create an Aurora cluster with a single writer instance and enable automatic backups.

Question 14

A company is migrating a 2 TB on-premises Microsoft SQL Server database to Amazon RDS for SQL Server. The migration must be completed with minimal downtime and the source database must remain online during the migration. Which AWS service or feature should be used to achieve this?

Accepted Answer

AWS Database Migration Service (AWS DMS) with ongoing replication.. AWS DMS with ongoing replication is designed for minimal-downtime migrations. It reads from the source's transaction logs to capture changes while the source remains online. The target RDS for SQL Server stays synchronized, and cutover can be quick, meeting the requirement.

Answer

AWS Snowball Edge to transfer the database backup, followed by restore.

Answer

Native SQL Server backup and restore to Amazon RDS for SQL Server.

Answer

SQL Server transactional replication to Amazon RDS for SQL Server.

Question 15

A company is planning to migrate an on-premises MySQL database to Amazon RDS for MySQL. The database is 500 GB and the company wants to minimize downtime. They have set up AWS DMS with a replication instance. During testing, they notice that the replication instance is not capturing changes from the source database. What is the most likely cause?

Accepted Answer

The source database binary logging is not enabled.. AWS DMS requires binary logging on MySQL sources to capture ongoing changes. Without it, CDC cannot function. The other options might cause different issues but not specifically prevent change capture. Ensuring binary logging is enabled with ROW format is essential for MySQL migrations with DMS.

Answer

The AWS DMS replication instance is under-provisioned.

Answer

The replication instance is in a different VPC than the target database.

Answer

The target database does not have sufficient storage.

Question 16

A healthcare company is building a new patient appointment scheduling system on AWS. The system must provide ACID transactions, support complex joins across patient, provider, and appointment tables, and be highly available across two Availability Zones. The expected load is moderate, with about 500 transactions per second. The company wants a fully managed relational database with automatic failover. Which AWS database solution best meets these requirements?

Accepted Answer

Amazon RDS for MySQL with a Multi-AZ deployment. The workload requires a relational engine with ACID transactions, complex joins, and automatic failover across Availability Zones. Amazon RDS for MySQL with Multi-AZ delivers a managed relational database with synchronous standby replication and automatic failover, matching the moderate transaction rate and availability needs. Other options either use non-relational models, lack multi-AZ failover, or are optimized for analytics rather than transactional scheduling.

Answer

Amazon DynamoDB with a global secondary index for each table

Answer

Amazon Redshift with a single-node cluster

Answer

Amazon Neptune with a read replica in a second Availability Zone

Question 17

A retail company runs an Amazon RDS for PostgreSQL database that supports an order management system. The database experiences unpredictable read spikes during flash sales. The team wants to offload read traffic and improve read scalability with minimal changes. Which solution should they implement?

Accepted Answer

Create one or more read replicas and direct read queries to them.. RDS read replicas are designed to offload read traffic from the primary instance. By creating one or more read replicas and directing read queries to them, the team can scale reads horizontally and handle flash-sale spikes without a major architectural change. This approach is simpler and more cost-effective than scaling up or migrating.

Answer

Enable Multi-AZ deployment for the RDS instance.

Answer

Increase the instance size of the primary RDS instance.

Answer

Migrate the database to Amazon DynamoDB to handle read spikes.

Question 18

A company is deploying a new web application that requires a relational database. The database will store user accounts, orders, and product inventory. The workload is expected to be moderate, with occasional spikes during sales events. The company wants a managed service that automatically handles backups, software patching, and replication across multiple Availability Zones. Which AWS service should they use?

Accepted Answer

Amazon RDS for MySQL with a Multi-AZ deployment. The company needs a managed relational database that handles backups, patching, and Multi-AZ replication. Amazon RDS for MySQL fits these requirements perfectly. It provides a familiar relational model, automated administration, and high availability through Multi-AZ deployments. The other options are either non-relational, analytical, or caching services that do not support transactional relational workloads.

Answer

Amazon DynamoDB with on-demand capacity

Answer

Amazon Redshift

Answer

Amazon ElastiCache for Memcached

Question 19

A retail company is deploying a new application that requires a database with extremely low latency for read-heavy workloads. The data model consists of key-value pairs and the application must scale horizontally to handle millions of requests per second. The company wants a fully managed solution with predictable performance. Which AWS service is BEST suited for this requirement?

Accepted Answer

Amazon DynamoDB with provisioned capacity and auto scaling. The workload demands low latency, horizontal scalability, and a key-value data model. Amazon DynamoDB is purpose-built for this, offering consistent single-digit millisecond latency, seamless scaling, and a fully managed experience. Other options either are not databases (ElastiCache), not optimized for key-value at scale (RDS), or serve a different data model (Neptune).

Answer

Amazon RDS for MySQL with read replicas

Answer

Amazon Neptune with read replicas

Answer

Amazon ElastiCache for Memcached

Question 20

A logistics company runs an Amazon Aurora MySQL cluster for its shipment tracking application. The application performs many small read queries per second and a moderate number of writes. The team wants to improve read scalability without changing application code, and they want to minimize replication lag. Which Aurora feature should they use?

Accepted Answer

Aurora Replicas. Aurora Replicas are read-only instances that share the same distributed storage volume as the writer. They provide read scaling with minimal replication lag because they do not need to replicate data pages; they only replicate metadata and log records. The application can use the reader endpoint to distribute reads. Aurora Global Database is for cross-Region scenarios, Multi-Master is for write scaling, and Serverless v1 is for variable workloads, so Aurora Replicas best fit the requirement.

Answer

Aurora Serverless v1

Answer

Aurora Multi-Master

Answer

Aurora Global Database