handler.py

import json
import boto3
from boto3.dynamodb.conditions import Key

def lambda_handler(event, context):
	client = boto3.resource('dynamodb')
	table = client.Table('Transactions')

	#1. Example - Get Item By Id

	response = table.get_item(
		Key={
			'TransactionType_OriginCountry': 'PURCHASE_USA',
			'Date': '2019-11-17'
		}
	)

	print(response['Item'])

	print('\n\n\n-----\n\n\n')

	#2. Example 2 - Query by Partition Key / Sort Key Criteria

	response = table.query(
		KeyConditionExpression=Key('TransactionType_OriginCountry').eq('PURCHASE_USA') & Key('Date').gt('2019-11-15')
	)

	items = response['Items']
	for item in items:
		print(item)

I was getting the same error as above. Found out since I was using index on my table, I had to specify...

response = table.query(
IndexName='clientId-meetingDate-index',
KeyConditionExpression=Key('clientId').eq('abc') & Key('meetingDate').gte('2022-05-05')
)

Of course change to your index, and attribute values, but after adding IndexName, all worked well.