Creating a DynamoDB table in AWS - Practice Exercises

Challenge - 5 Problems

❓ Configuration

intermediate

DynamoDB Table Partition Key Type

You want to create a DynamoDB table with a partition key named CustomerId that stores string values. Which option correctly defines the partition key attribute in the AWS CLI command?

A aws dynamodb create-table --table-name Customers --attribute-definitions AttributeName=CustomerId,AttributeType=S --key-schema AttributeName=CustomerId,KeyType=HASH --provisioned-throughput ReadCapacityUnits=5,WriteCapacityUnits=5

B aws dynamodb create-table --table-name Customers --attribute-definitions AttributeName=CustomerId,AttributeType=BOOL --key-schema AttributeName=CustomerId,KeyType=HASH --provisioned-throughput ReadCapacityUnits=5,WriteCapacityUnits=5

C aws dynamodb create-table --table-name Customers --attribute-definitions AttributeName=CustomerId,AttributeType=B --key-schema AttributeName=CustomerId,KeyType=HASH --provisioned-throughput ReadCapacityUnits=5,WriteCapacityUnits=5

D aws dynamodb create-table --table-name Customers --attribute-definitions AttributeName=CustomerId,AttributeType=N --key-schema AttributeName=CustomerId,KeyType=HASH --provisioned-throughput ReadCapacityUnits=5,WriteCapacityUnits=5

💡 Hint

The partition key type must match the data type you plan to store. 'S' stands for string.

DynamoDB attribute types include 'S' for string, 'N' for number, and 'B' for binary. 'BOOL' is not a valid attribute type for keys. Since CustomerId stores strings, 'S' is correct.

❓ Architecture

intermediate

Choosing a Sort Key for Efficient Queries

You are designing a DynamoDB table to store orders. Each order has a unique OrderId and a timestamp when it was placed. You want to efficiently query all orders for a customer sorted by time. Which key schema is best?

A Partition key: OrderTimestamp (number), Sort key: CustomerId (string)

B Partition key: OrderId (string), Sort key: CustomerId (string)

C Partition key: CustomerId (string), Sort key: OrderTimestamp (number)

D Partition key: CustomerId (string) only, no sort key

💡 Hint

Think about how to group orders by customer and sort them by time.

Using CustomerId as partition key groups all orders per customer. Adding OrderTimestamp as sort key allows sorting orders by time within each customer group.

❓ security

advanced

IAM Policy for DynamoDB Table Access

You want to create an IAM policy that allows read-only access to a DynamoDB table named Orders. Which policy statement correctly grants this permission?

A {"Effect": "Allow", "Action": ["dynamodb:PutItem", "dynamodb:UpdateItem"], "Resource": "arn:aws:dynamodb:*:*:table/Orders"}

B {"Effect": "Allow", "Action": ["dynamodb:DeleteItem"], "Resource": "arn:aws:dynamodb:*:*:table/Orders"}

C {"Effect": "Deny", "Action": ["dynamodb:GetItem"], "Resource": "arn:aws:dynamodb:*:*:table/Orders"}

D {"Effect": "Allow", "Action": ["dynamodb:GetItem", "dynamodb:Query", "dynamodb:Scan"], "Resource": "arn:aws:dynamodb:*:*:table/Orders"}

💡 Hint

Read-only actions include GetItem, Query, and Scan.

To allow read-only access, the policy must allow GetItem, Query, and Scan actions. PutItem, UpdateItem, and DeleteItem are write actions. Deny effect blocks access.

❓ service_behavior

advanced

DynamoDB Provisioned Throughput Behavior

You create a DynamoDB table with provisioned throughput of 5 read capacity units and 5 write capacity units. What happens if your application suddenly tries to perform 20 writes per second?

A DynamoDB queues the extra write requests and processes them later without errors.

B DynamoDB throttles the write requests exceeding 5 per second, causing some requests to fail with a ProvisionedThroughputExceededException.

C All 20 write requests succeed without delay or error.

D DynamoDB automatically increases the write capacity units to 20 to handle the load.

💡 Hint

Provisioned throughput limits the number of reads and writes per second.

If the application exceeds provisioned capacity, DynamoDB throttles excess requests and returns errors. It does not auto-scale unless auto-scaling is configured.

✅ Best Practice

expert

Designing a DynamoDB Table for High Write Throughput

You expect a very high number of writes per second to your DynamoDB table. Which design choice helps avoid hot partitions and ensures even write distribution?

A Use a partition key with high cardinality and add a random suffix to distribute writes evenly.

B Use a single fixed partition key value for all items to simplify queries.

C Use only a sort key without a partition key to distribute writes.

D Use a partition key with low cardinality and rely on sort key for uniqueness.

💡 Hint

Think about how DynamoDB partitions data and distributes load.

DynamoDB partitions data by partition key. High cardinality keys spread writes across partitions. Adding randomness helps avoid hot spots. Single fixed keys cause hot partitions.

Practice

1. What is the main purpose of the primary key when creating a DynamoDB table?

easy

A. To define the table's read capacity

B. To store the table's name

C. To specify the AWS region

D. To uniquely identify each item in the table

Solution

1. Step 1: Understand the role of the primary key

   The primary key uniquely identifies each item in a DynamoDB table, ensuring no duplicates.

2. Step 2: Differentiate from other table properties

   Table name, capacity, and region do not serve as unique identifiers for items.

3. Final Answer:

   To uniquely identify each item in the table -> Option D

4. Quick Check:

   Primary key = unique item ID [OK]

Hint: Primary key means unique ID for each item [OK]

Common Mistakes:

• Confusing primary key with table name
• Thinking capacity defines uniqueness
• Mixing region with key attributes

2. Which AWS CLI command correctly creates a DynamoDB table named Users with a primary key UserId of type string?

easy

A. aws dynamodb create-table --table-name Users --attribute-definitions AttributeName=UserId,AttributeType=S --key-schema AttributeName=UserId,KeyType=HASH --provisioned-throughput ReadCapacityUnits=5,WriteCapacityUnits=5

B. aws dynamodb create-table --name Users --key UserId --type String

C. aws dynamodb make-table --table Users --key UserId --type S

D. aws dynamodb create-table --table Users --attribute UserId String --key UserId HASH

Solution

1. Step 1: Identify correct AWS CLI syntax for creating a table

   The correct command uses create-table with --table-name, --attribute-definitions, --key-schema, and --provisioned-throughput.

2. Step 2: Verify attribute and key schema details

   AttributeName=UserId with AttributeType=S (string) and KeyType=HASH for primary key is correct.

3. Final Answer:

   aws dynamodb create-table --table-name Users --attribute-definitions AttributeName=UserId,AttributeType=S --key-schema AttributeName=UserId,KeyType=HASH --provisioned-throughput ReadCapacityUnits=5,WriteCapacityUnits=5 -> Option A

4. Quick Check:

   Correct CLI syntax = aws dynamodb create-table --table-name Users --attribute-definitions AttributeName=UserId,AttributeType=S --key-schema AttributeName=UserId,KeyType=HASH --provisioned-throughput ReadCapacityUnits=5,WriteCapacityUnits=5 [OK]

Hint: Use --attribute-definitions and --key-schema for keys [OK]

Common Mistakes:

• Using wrong command like make-table
• Missing provisioned throughput
• Incorrect flags like --name instead of --table-name

3. Given this AWS CLI command:

aws dynamodb create-table --table-name Products --attribute-definitions AttributeName=ProductId,AttributeType=S AttributeName=Category,AttributeType=S --key-schema AttributeName=ProductId,KeyType=HASH AttributeName=Category,KeyType=RANGE --provisioned-throughput ReadCapacityUnits=10,WriteCapacityUnits=5

What is the primary key type of the Products table?

medium

A. No primary key defined

B. Simple primary key with only a HASH key

C. Composite primary key with HASH and RANGE keys

D. Primary key with only a RANGE key

Solution

1. Step 1: Analyze the key schema in the command

   The command defines two keys: ProductId as HASH and Category as RANGE.

2. Step 2: Understand primary key types in DynamoDB

   A primary key with both HASH and RANGE keys is called a composite primary key.

3. Final Answer:

   Composite primary key with HASH and RANGE keys -> Option C

4. Quick Check:

   HASH + RANGE = composite key [OK]

Hint: HASH + RANGE keys mean composite primary key [OK]

Common Mistakes:

• Thinking two attributes mean no key
• Confusing RANGE key as standalone primary key
• Ignoring key-schema details

4. You run this command to create a DynamoDB table:

aws dynamodb create-table --table-name Orders --attribute-definitions AttributeName=Id,AttributeType=N --key-schema AttributeName=OrderId,KeyType=HASH --provisioned-throughput ReadCapacityUnits=5,WriteCapacityUnits=5

But you get an error. What is the most likely cause?

medium

A. The attribute definition and key schema attribute names do not match

B. Provisioned throughput values are missing

C. The key schema is missing a RANGE key

D. AttributeType should be 'S' for string, not 'N' for number

Solution

1. Step 1: Check attribute definitions and key schema names

   The attribute definitions specify AttributeName=Id, but the key schema specifies AttributeName=OrderId. The names do not match, causing the error.

2. Step 2: Verify other potential issues

   Provisioned throughput values are present (not B), a simple primary key with only HASH is allowed (not C), AttributeType=N is valid for numeric IDs (not D).

3. Final Answer:

   The attribute definition and key schema attribute names do not match -> Option A

4. Quick Check:

   Attribute names must match exactly [OK]

Hint: Match attribute names exactly in definitions and key schema [OK]

Common Mistakes:

• Assuming 'N' type is invalid
• Expecting RANGE key for all tables
• Missing provisioned throughput

5. You want to create a DynamoDB table named Sessions with a composite primary key: UserId (string) as HASH and SessionId (string) as RANGE. You also want to set autoscaling for read and write capacity. Which of the following is the best approach?

hard

A. Create the table without specifying key schema and add keys later

B. Use aws dynamodb create-table with attribute definitions and key schema, then configure autoscaling via Application Auto Scaling service

C. Use aws dynamodb create-table with only HASH key and enable autoscaling in the same command

D. Create the table with fixed provisioned throughput and manually update capacity when needed

Solution

1. Step 1: Define table with composite primary key

   Use create-table with attribute definitions for UserId and SessionId, and key schema with HASH and RANGE keys.

2. Step 2: Configure autoscaling separately

   DynamoDB autoscaling is set up via Application Auto Scaling service after table creation; it cannot be enabled directly in create-table command.

3. Final Answer:

   Use aws dynamodb create-table with attribute definitions and key schema, then configure autoscaling via Application Auto Scaling service -> Option B

4. Quick Check:

   Composite key + separate autoscaling setup = Use aws dynamodb create-table with attribute definitions and key schema, then configure autoscaling via Application Auto Scaling service [OK]

Hint: Create table first, then set autoscaling separately [OK]

Common Mistakes:

• Trying to enable autoscaling in create-table command
• Skipping RANGE key for composite key
• Creating table without key schema