javascript query last items in dynamodb from aws lambda

So I have a dynamodb table with a primary key ID and a secondary key Time which is a number/timestamp. Now I want to query the latest record of a particular ID. I tried to construct the parameters like this but don’t know how to move forward to query the item with the largest Time.

function get_snapshot(id, callback){
    let params = {
        TableName: "Table1",
        KeyConditionExpression: "ID = :id and Time ", // here I stuck
        ExpressionAttributeValues: {
        ":id": id
        }
    }; 
    docClient.query(params, function(err, data){
        ... // process the fetched item here
    })
}

I’m quite new to this field. There could be a lot of rookie mistakes. Any help is appreciated.

Answer

You don’t actually need Time in the key condition for your query. If you want to get the 10 latest items, for example, your query params should look like this:

let params = {
    TableName: "Table1",
    KeyConditionExpression: "ID = :id",
    ExpressionAttributeValues: {
        ":id": id
    },
    ScanIndexForward: "false",
    Limit: 1
}; 

ScanIndexForward: false tells DynamoDB that it should return results starting with the highest sort key value. Limit: 1 tells DynamoDB that you only want to get the first 1 results.

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