AWS Lambda and AWS API Gateway: How to send a binary file?

Question

I have a lambda function which fetches a file from s3 using the input key in event and needs to send the same to client. I am using the following function to get the file from s3

function getObject(key){
  var params = {
    Bucket: "my_bucket",
    Key: key   
  }
  return new Promise(function (resolve, reject){
    s3.getObject(params, function (err, data){
      if(err){
        reject(err);
      }
      resolve(data.Body)
    })
  })
}

If I send the response of this promise (buffer) to context.succeed , it is displayed as a JSON array on front end. How can I send it as a file ? The files can be either ZIP or HTTP Archive (HAR) files. The s3 keys contain the appropriate extension. I am guessing it has got something to do with the "Integration Response" in API Gateway. But not able to figure out where to change

Answer 1

Good news, you can now handle binary input and output for API Gateway ( announcement and documentation ).

Basically, nothing changes in your Lambda Function, but you can now set the contentHandling API Gateway Integration property to CONVERT_TO_BINARY .

Unfortunately, the official AWS examples showcase only the HTTP API Gateway backend, as the AWS Lambda support seems not complete yet. For example, I haven't managed to return gzipped content from AWS Lambda yet, although it should be possible thanks to the new binary support and the $util.base64Decode() mapping utility.