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Hard Difficulty Questions

Practise AWS Certified Database Specialty DBS-C01 practice questions — original exam-style scenarios covering every exam domain, with detailed explanations, wrong-answer analysis, and common exam traps.

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DBS-C01
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Amazon Web Services
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Scenario guide

How to approach hard difficulty questions

These are the questions most candidates get wrong. They require connecting multiple concepts, reading tricky output, or knowing edge-case behaviour that isn't on most study cards. Practising them trains you to operate under uncertainty — a necessary skill on the real exam.

Quick answer

Hard Difficulty Questions questions test whether you can apply the concept in context, not just recognise a definition.

How the topic appears in realistic exam-style scenarios.

Which detail in the question changes the correct answer.

How to eliminate plausible but wrong options.

How to connect the question back to the wider exam objective.

Related practice questions

Related DBS-C01 topic practice pages

Scenario questions usually connect to one or more exam topics. Use these links to review the underlying concepts behind the scenario.

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Management and Operations practice questions

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Monitoring and Troubleshooting practice questions

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Database Security practice questions

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DBS-C01 fundamentals practice questions

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DBS-C01 scenario practice questions

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DBS-C01 troubleshooting practice questions

Practise DBS-C01 questions linked to DBS-C01 troubleshooting.

Practice set

Practice scenarios

Question 1hardmultiple choice
Full question →

A team is using AWS DMS to migrate a 3 TB Oracle database to Amazon Aurora PostgreSQL. They configured the task as shown. After the full load completes, they notice that the target tables have no indexes, primary keys, or foreign keys. What is the most likely cause?

Exhibit

Refer to the exhibit.

-- AWS DMS Migration Task JSON excerpt:
{
  "MigrationType": "full-load",
  "TableMappings": {
    "rules": [
      {
        "rule-type": "selection",
        "rule-id": "1",
        "rule-name": "1",
        "object-locator": {
          "schema-name": "%",
          "table-name": "%"
        },
        "rule-action": "include"
      }
    ]
  },
  "TargetTablePrepMode": "DROP_AND_CREATE"
}
Question 2hardmultiple choice
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A company is migrating an on-premises Microsoft SQL Server database to Amazon RDS for SQL Server. The database uses SQL Server Agent jobs, custom CLR assemblies, and cross-database queries. Which of the following will require modification before migration?

Question 3hardmulti select
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A company is running a production Amazon DynamoDB table with on-demand capacity. The table experiences occasional throttling during traffic spikes. The table's partition key is a timestamp, and the workload is write-heavy. The operations team needs to reduce throttling. Which THREE actions should the team take? (Choose three.)

Question 4hardmulti select
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A company is migrating its on-premises Oracle database to Amazon RDS for Oracle. The database specialist needs to monitor the migration process and ensure data consistency. Which TWO AWS services should be used together to continuously monitor the replication lag and data integrity?

Question 5hardmultiple choice
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A database engineer is reviewing Amazon RDS for MySQL error logs and sees repeated authentication failures from the same IP address. The application team confirms the password is correct. What is the most likely cause of these errors?

Exhibit

Refer to the exhibit.

From Amazon CloudWatch Logs:

2023-04-01T12:00:00Z [ERROR] [Client] Authentication failed for user 'app_user' from host '10.0.1.50' using method 'mysql_native_password'
2023-04-01T12:01:00Z [ERROR] [Client] Access denied for user 'app_user'@'10.0.1.50' (using password: YES)
2023-04-01T12:02:00Z [ERROR] [Client] Access denied for user 'app_user'@'10.0.1.50' (using password: YES)
Question 6hardmultiple choice
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Refer to the exhibit. A security engineer has applied this key policy to a customer managed KMS key used to encrypt a Secrets Manager secret containing database credentials. An application running on an Amazon EC2 instance in the same account and region is unable to decrypt the secret. What is the MOST likely cause?

Exhibit

Refer to the exhibit.

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": "kms:Decrypt",
      "Resource": "arn:aws:kms:us-east-1:123456789012:key/abc12345-...",
      "Condition": {
        "StringEquals": {
          "kms:ViaService": "secretsmanager.us-east-1.amazonaws.com",
          "kms:CallerAccount": "123456789012"
        }
      }
    }
  ]
}
Question 7hardmultiple choice
Full question →

A security engineer is troubleshooting an issue where an application using IAM role 'app-role' with a trust policy to assume the 'app-user' user is unable to decrypt an RDS database that uses a customer-managed KMS key. The above key policy is attached to the KMS key. What is the likely cause of the failure?

Exhibit

Refer to the exhibit.

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "AllowRoot",
      "Effect": "Allow",
      "Principal": {
        "AWS": "arn:aws:iam::123456789012:root"
      },
      "Action": "kms:*",
      "Resource": "*"
    },
    {
      "Sid": "AllowAppUser",
      "Effect": "Allow",
      "Principal": {
        "AWS": "arn:aws:iam::123456789012:user/app-user"
      },
      "Action": [
        "kms:Decrypt",
        "kms:GenerateDataKey"
      ],
      "Resource": "*",
      "Condition": {
        "StringEquals": {
          "kms:ViaService": "rds.us-east-1.amazonaws.com"
        }
      }
    }
  ]
}
Question 8hardmultiple choice
Full question →

A database specialist sees the above error log entries from an Amazon RDS for MySQL DB instance. Which action should be taken to resolve the issue?

Exhibit

Refer to the exhibit. A database specialist receives the following Amazon CloudWatch Logs excerpt from an Amazon RDS for MySQL DB instance:

2024-11-15 10:23:45 UTC [ERROR] [MY-013118] [InnoDB] Page [page id: space=5, page number=1234] log sequence number 567890 is in the future! Current system log sequence number 567800.
2024-11-15 10:23:46 UTC [ERROR] [MY-011825] [InnoDB] Unable to purge a record because it is in a non-tablespace page.
2024-11-15 10:24:01 UTC [ERROR] [MY-013114] [InnoDB] Database page corruption on disk or a failed file read of page [page id: space=5, page number=1235]. You may have to recover from a backup.
Question 9hardmultiple choice
Read the full NAT/PAT explanation →

A social media analytics company uses Amazon DynamoDB as the primary data store for user session data. Each session record has a partition key of user_id (String) and a sort key of session_start_time (Number, epoch). The application often queries the most recent 10 sessions for a given user. The traffic pattern shows that 90% of reads are for the last 10 sessions, while 10% are for historical sessions. The table has a provisioned read capacity of 5000 RCU and consistently experiences throttled read requests during peak hours. The company wants to optimize read performance without changing the provisioned capacity. Which design change will MOST improve read performance for this workload?

Question 10hardmultiple choice
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A company is designing a new e-commerce platform using Amazon DynamoDB. The workload requires single-digit millisecond latency for user session data, which is accessed by session token. The session data is temporary and should be automatically deleted after 24 hours. Which DynamoDB design should the database specialist recommend?

Question 11hardmulti select
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A company is designing a multi-tenant SaaS application on Amazon Aurora MySQL. Each tenant has its own database, but some tenants are very large and generate high write traffic. The company wants to isolate tenant workloads to prevent a noisy neighbor from affecting other tenants. Which TWO design strategies should the database specialist recommend?

Question 12hardmultiple choice
Full question →

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?

Question 13hardmultiple choice
Full question →

A database specialist is analyzing an Aurora MySQL error log and finds the above deadlock error. The application performs an update on the orders table and then updates the inventory table within the same transaction. The deadlock occurs when two concurrent transactions try to update orders and inventory in different orders. Which design change should the database specialist recommend to reduce deadlocks?

Exhibit

Refer to the exhibit.

```
2024-03-15 10:23:45 UTC | aurora-db-instance-1: Aurora MySQL
2024-03-15 10:23:45 UTC | 10.0.1.5:12345 [3] [thread 1] [transaction 1234]
2024-03-15 10:23:45 UTC | ERROR: Deadlock found when trying to get lock; try restarting transaction
2024-03-15 10:23:45 UTC |  at line 1: UPDATE orders SET status='shipped' WHERE order_id=1001;
2024-03-15 10:23:45 UTC |  at line 2: UPDATE inventory SET quantity=quantity-1 WHERE product_id=500;
```
Question 14hardmulti select
Full question →

A company runs a customer relationship management (CRM) application on Amazon RDS for PostgreSQL. The application has a table 'customers' with columns: id (primary key), name, email, signup_date, and status. The table has 10 million rows. The application frequently queries by email address. The company also needs to run analytical queries that aggregate customers by signup_date and status. The DBA notices that the index on email is heavily used and causes high write latency. The company wants to improve write performance without sacrificing read performance for email queries. Which THREE actions should the database specialist take? (Choose THREE.)

Question 15hardmultiple choice
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A financial services company is designing a ledger system using Amazon QLDB. The application records transactions that must never be modified or deleted. The company expects high write throughput and needs to ensure that the ledger can handle the load without throttling. Which design consideration is MOST important to achieve this?

Question 16hardmultiple choice
Read the full NAT/PAT explanation →

A social media company uses Amazon DynamoDB to store user posts. The table has a partition key of 'user_id' and a sort key of 'post_timestamp'. Each item is about 10 KB. The application needs to retrieve all posts for a given user within a date range. The company recently added a new feature that allows users to 'like' posts, and they store the like count as an attribute in the post item. The like count is updated frequently. The application experiences high write throttling on the table. The table has 1000 WCUs provisioned. The write pattern is bursty. Which design change would MOST effectively reduce write throttling?

Question 17hardmultiple choice
Full question →

A financial services company uses Amazon RDS for MySQL to store transaction data. The database has a single table 'transactions' with 500 million rows. The table has an auto-increment primary key and an index on 'transaction_date'. The company runs a monthly report that aggregates transactions by account_id and transaction_date. The report query uses a GROUP BY on account_id and transaction_date, and scans the entire table. The query takes over 2 hours to complete and often times out. The DBA suggests creating a materialized view. However, the company wants to minimize operational overhead. Which solution meets the requirements with the LEAST operational overhead?

Question 18hardmultiple choice
Full question →

A company is using AWS Database Migration Service (AWS DMS) to migrate a 5 TB MySQL database to Amazon RDS for MySQL. The migration is taking longer than expected. The company notices that the source database has a high volume of write operations. Which configuration change would MOST likely improve the migration performance?

Question 19hardmultiple choice
Full question →

A company is migrating a self-managed Oracle database to Amazon Aurora PostgreSQL using AWS DMS. The source database has a large number of tables with foreign key constraints. During the full load phase, some tables fail to load due to foreign key violations. What is the most efficient way to resolve this?

Question 20hardmultiple choice
Full question →

A team is setting up a DMS migration task. The IAM policy above is attached to the DMS replication instance's IAM role. The team is unable to modify the target RDS instance's maintenance window during the migration. Which additional permission is missing?

Exhibit

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": [
        "dms:CreateEndpoint",
        "dms:ModifyEndpoint",
        "dms:DescribeEndpoints"
      ],
      "Resource": "*"
    },
    {
      "Effect": "Allow",
      "Action": [
        "rds:DescribeDBInstances",
        "rds:ModifyDBInstance"
      ],
      "Resource": "arn:aws:rds:us-east-1:123456789012:db:target-db"
    }
  ]
}

These DBS-C01 practice questions are part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style DBS-C01 questions with detailed explanations, topic-based practice, mock exams, readiness tracking, and study analytics.