Query:

• Uses primary key or index keys
• Retrieves specific items efficiently
• Lower cost and better performance
• Can use filter expressions for additional filtering

Scan:

• Examines every item in table/index
• Expensive and slow for large tables
• Uses filter expressions to return subset
• Should be avoided in production for large datasets

# Query example
response = table.query(
    KeyConditionExpression=Key('user_id').eq('123')
)

# Scan example  
response = table.scan(
    FilterExpression=Attr('age').gt(21)
)