Design DynamoDB for Large data using array. Over 400k

I'm worked with node.js and for record event-time and event-data, I want to use AWS DynamoDB Table.

single data and one-key-data schema sample like under.

var want_to_update_data = [ // contain json more or same than 1
  { "event-time" : "2021-01-02 10:11:12", "event-data" : 19 },
  ...
];

var saved_data = { // DynamoDB Saved Data Sample with Key "ABCD"
  "Key" : "ABCD",
  "events" : [
    ...
    { "event-time" : "2020-12-28 09:30:17", "event-data" : 35 },
    { "event-time" : "2021-01-01 19:11:12", "event-data" : 16 },
    { "event-time" : "2021-01-02 10:11:12", "event-data" : 19 },
    ...
  ]
}

Upper data is only for sample. json contains more key-values.

For update single json, my server code likes under.

app.get('/insert', req, res) {
  var update_key = req.body.update_key; // "ABCD"
  var want_to_update_data = req.body.update_data; // [ {} ]

  var updateExpression = 'SET events = list_append(events, :dl)'; // dl means data-list
  var expressionAttributeValues = {':dl' : want_to_update_data }; // dl means data-list

  AWS.config.update({
    region: "region",
    endpoint: "endpoint",
    accessKeyId: "access_key",
    secretAccessKey: "secret_key",
  });

  var params = {
    TableName: "TableName",
    Key: update_key,
    UpdateExpression: updateExpression,
    ExpressionAttributeValues: expressionAttributeValues,
    ReturnValues: "UPDATED_NEW"
  });

  var dynamodbClient = new AWS.DynamoDB.DocumentClient();
  dynamodbClient.update(params, function(err, data) {
    if(err) { /* handle error */ }
    else { /* handle after update complete */ }
  });
});

Simply, It works, but AWS DynamoDB can't change over 4kb at once.
So, if array data is bigger than 4k, list_append not worked with ValidationException: Item size to update has exceeded the maximum allowed size error message.

I want to remain all events and want to sort event-time keys.

How can I change my DynamoDB schema?

Under code is just my guess.
Is it possible?

{
  "Key" : "ABCD",
  /*
  "events" : [
    ...
    { "event-time" : "2020-12-28 09:30:17", "event-data" : 35 },
    { "event-time" : "2021-01-01 19:11:12", "event-data" : 16 },
    { "event-time" : "2021-01-02 10:11:12", "event-data" : 19 },
    ...
  ]
  */
  "events" : { // is it possible events['some-date'] could be sort-key?
    ...
    "2020-12-28 09:30:17" : 35,
    "2021-01-01 19:11:12" : 16,
    "2021-01-02 10:11:12" : 19,
    ...
  }

}

/*
  var updateExpression = 'SET events = list_append(events, :dl)'; // dl means data-list
  var expressionAttributeValues = {':dl' : want_to_update_data }; // dl means data-list
*/

  // under 2 line is just for sample. json key is not fixed
  var event_time = '2021-01-02 10:11:12';
  var single_json = want_to_update_data[event_time];

  // if number-start key is not allow(event_time), prefix append could be like "D_2021~~"
  var updateExpression = `SET events.${event_time} = :dl`;
  var expressionAttributeValues = {':dl' : single_json }; // single json

Thank you for read my question.

I want to create new table for save my events json datas. (not S3. using DynamoDB)