Are Dynamodb conditional expressions consistent across nodes?

Question

I am trying to lock an object in a table with a function that looks like this:

def lock():
    dynamodb = boto3.resource('dynamodb', endpoint_url="http://localhost:8000")

table = dynamodb.Table('table')

response = table.update_item(
        Key={
            'id': "id1",
            'created_at': "2022-02-06T12:07:45.602721617Z"
        },
        UpdateExpression="SET #O.L  = :locked",
        ConditionExpression="object.locked <> :locked",
        ExpressionAttributeValues={':locked': True},
        ReturnValues="UPDATED_NEW"
    )
    return response

Given that several workers might be trying to get the lock at the same time and there is no way to have consistent write in Dynamodb. Is it possible for multiple workers to acquire the lock at the same time?

Leeroy Hannigan · Accepted Answer

All writes to DynamoDB are singleton and consistent. There is only a chance for a single thread to acquire the lock, all others will fail. More here.

Reads on the other hand can be both Eventually Consistent or optionally Strongly Consistent. More here.

Reads on the other hand can be both Eventually Consistent or optionally Strongly Consistent. More [here](https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/HowItWorks.ReadConsistency.html).

Are Dynamodb conditional expressions consistent across nodes?

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