Scan vs Query performance comparison in DynamoDB - Hands-On Comparison

Scan vs Query Performance Comparison in DynamoDB

📖 Scenario: You are managing a DynamoDB table that stores customer orders. You want to understand the difference in performance between using Scan and Query operations to retrieve data.

🎯 Goal: Build a simple DynamoDB setup with a table of orders, then write code to perform a Scan and a Query operation. Compare how each operation works and understand their performance differences.

📋 What You'll Learn

Create a DynamoDB table named Orders with OrderId as the partition key

Insert 5 sample orders with specific OrderId and CustomerName

Define a variable to hold the CustomerName to query

Write a Query operation to get orders for the given CustomerName

Write a Scan operation to get all orders and filter by CustomerName

💡 Why This Matters

🌍 Real World

Understanding the difference between Scan and Query helps optimize database performance and cost in real DynamoDB applications.

💼 Career

Database developers and cloud engineers often need to choose the right DynamoDB operation to efficiently retrieve data.

1

Create the Orders table with sample data

Create a dictionary called orders with these exact entries representing orders: 'OrderId': 101, 'CustomerName': 'Alice', 'OrderId': 102, 'CustomerName': 'Bob', 'OrderId': 103, 'CustomerName': 'Alice', 'OrderId': 104, 'CustomerName': 'Charlie', 'OrderId': 105, 'CustomerName': 'Bob'. Store these as a list of dictionaries in orders.

DynamoDB

# Create the orders list with 5 dictionaries
# Your code here

Need a hint?

Use a list of dictionaries. Each dictionary has keys 'OrderId' and 'CustomerName'.

2

Set the customer name to query

Create a variable called customer_to_find and set it to the string 'Bob'.

DynamoDB

orders = [
    {'OrderId': 101, 'CustomerName': 'Alice'},
    {'OrderId': 102, 'CustomerName': 'Bob'},
    {'OrderId': 103, 'CustomerName': 'Alice'},
    {'OrderId': 104, 'CustomerName': 'Charlie'},
    {'OrderId': 105, 'CustomerName': 'Bob'}
]
# Create the variable customer_to_find with value 'Bob'
# Your code here

Need a hint?

Just assign the string 'Bob' to the variable customer_to_find.

3

Write the Query operation to find orders for Bob

Create a list called query_results that contains only the orders from orders where CustomerName equals customer_to_find. Use a list comprehension with order as the loop variable.

DynamoDB

orders = [
    {'OrderId': 101, 'CustomerName': 'Alice'},
    {'OrderId': 102, 'CustomerName': 'Bob'},
    {'OrderId': 103, 'CustomerName': 'Alice'},
    {'OrderId': 104, 'CustomerName': 'Charlie'},
    {'OrderId': 105, 'CustomerName': 'Bob'}
]

customer_to_find = 'Bob'
# Use a list comprehension to create query_results with orders where CustomerName == customer_to_find
# Your code here

Need a hint?

Use a list comprehension with order in orders and filter by order['CustomerName'] == customer_to_find.

4

Write the Scan operation to find orders for Bob

Create a list called scan_results that contains all orders from orders but filtered by CustomerName equal to customer_to_find. Use a for loop with order as the loop variable and an if statement inside the loop to append matching orders to scan_results.

DynamoDB

orders = [
    {'OrderId': 101, 'CustomerName': 'Alice'},
    {'OrderId': 102, 'CustomerName': 'Bob'},
    {'OrderId': 103, 'CustomerName': 'Alice'},
    {'OrderId': 104, 'CustomerName': 'Charlie'},
    {'OrderId': 105, 'CustomerName': 'Bob'}
]

customer_to_find = 'Bob'

query_results = [order for order in orders if order['CustomerName'] == customer_to_find]

# Use a for loop to create scan_results filtering orders by CustomerName == customer_to_find
# Your code here

Need a hint?

Initialize scan_results as an empty list. Use a for loop over orders. Inside the loop, use an if statement to check order['CustomerName'] == customer_to_find. Append matching orders to scan_results.