Partition key and sort key in AWS - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Partition Key Uniqueness

In a DynamoDB table, what does the partition key uniquely identify?

A The timestamp when the item was created

B A unique item in the table regardless of sort key

C The order in which items are stored physically

D A group of items that share the same partition key value

💡 Hint

Think about how partition keys group data in DynamoDB.

The partition key groups items into partitions. Multiple items can share the same partition key but differ by sort key.

❓ Architecture

intermediate

Choosing Keys for Efficient Queries

You want to design a DynamoDB table to store customer orders. Each customer can have multiple orders. Which key design allows efficient retrieval of all orders for a single customer?

A Partition key: OrderID, Sort key: CustomerID

B Partition key: CustomerName, Sort key: OrderDate

C Partition key: CustomerID, Sort key: OrderID

D Partition key: OrderDate, Sort key: CustomerID

💡 Hint

Think about grouping orders by customer for fast lookup.

Using CustomerID as partition key groups all orders per customer. Sort key OrderID uniquely identifies each order within that customer.

❓ service_behavior

advanced

Effect of Missing Sort Key in Composite Key Table

In a DynamoDB table with a composite primary key (partition key + sort key), what happens if you try to put an item without specifying the sort key?

A The operation fails with a validation error

B The item overwrites an existing item with the same partition key

C The item is stored with a null sort key value

D The item is stored but cannot be queried

💡 Hint

Consider the requirement of composite keys in DynamoDB.

DynamoDB requires both partition and sort keys for tables with composite keys. Missing sort key causes a validation error.

❓ security

advanced

Access Control Using Partition Key in IAM Policies

You want to restrict users to access only items with a specific partition key value in a DynamoDB table. Which IAM policy condition key helps enforce this?

A dynamodb:Attributes

B dynamodb:LeadingKeys

C dynamodb:Select

D dynamodb:ReturnConsumedCapacity

💡 Hint

Look for a condition key related to partition key values.

The dynamodb:LeadingKeys condition key restricts access to items with specified partition key values.

✅ Best Practice

expert

Designing Partition and Sort Keys for Hot Partition Avoidance

You have a DynamoDB table storing IoT sensor data with a high write rate. Which key design helps avoid hot partitions?

A Partition key: SensorID#Date, Sort key: Timestamp

B Partition key: Date, Sort key: SensorID

C Partition key: Timestamp, Sort key: SensorID

D Partition key: SensorID, Sort key: Timestamp

💡 Hint

Think about spreading writes across partitions by combining keys.

Combining SensorID and Date in partition key distributes writes across partitions daily, reducing hot partition risk.