可以在 Appsync schema 中定义查询参数以及使用 DynamoDB 的索引来优化查询。例如，在 Appsync schema 中定义参数：

type Query {
  listItems(
    filter: ModelItemFilterInput
    limit: Int
    nextToken: String
  ): ModelItemListConnection
}

并在 DynamoDB 中创建索引来支持查询：

{
  "TableName": "MyTable",
  "AttributeDefinitions": [
    {
      "AttributeName": "itemId",
      "AttributeType": "S"
    },
    {
      "AttributeName": "category",
      "AttributeType": "S"
    }
  ],
  "KeySchema": [
    {
      "AttributeName": "itemId",
      "KeyType": "HASH"
    },
    {
      "AttributeName": "category",
      "KeyType": "RANGE"
    }
  ],
  "GlobalSecondaryIndexes": [
    {
      "IndexName": "MyIndex",
      "KeySchema": [
        {
          "AttributeName": "category",
          "KeyType": "HASH"
        },
        {
          "AttributeName": "itemId",
          "KeyType": "RANGE"
        }
      ],
      "Projection": {
        "ProjectionType": "ALL"
      },
      "ProvisionedThroughput": {
        "ReadCapacityUnits": 5,
        "WriteCapacityUnits": 5
      }
    }
  ],
  "ProvisionedThroughput": {
    "ReadCapacityUnits": 5,
    "WriteCapacityUnits": 5
  }
}

这将在 DynamoDB 中创建一个名为“MyIndex”的全局二级索引，该索引按照“category”和“itemId”排序，以此支持按“category”和“itemId”字段查询并执行更高效的操作。