Query condition missed key schema element : Validation Error

I am trying to query dynamodb using the following code:

const AWS = require('aws-sdk');

let dynamo = new AWS.DynamoDB.DocumentClient({
  service: new AWS.DynamoDB(
    {
      apiVersion: "2012-08-10",
      region: "us-east-1"
    }),
  convertEmptyValues: true
});

dynamo.query({
  TableName: "Jobs",
  KeyConditionExpression: 'sstatus = :st',
  ExpressionAttributeValues: {
    ':st': 'processing'
  }
}, (err, resp) => {
  console.log(err, resp);
});

When I run this, I get an error saying:

ValidationException: Query condition missed key schema element: id

I do not understand this. I have defined id as the partition key for the jobs table and need to find all the jobs that are in processing status.