Lambda processing same SNS event multiple times?

From Amazon lambda FAQs page https://aws.amazon.com/lambda/faqs/

Q: What happens if my Lambda function fails during processing an event?

On failure, Lambda functions being invoked synchronously will respond with an exception. Lambda functions being invoked asynchronously are retried at least 3 times, after which the event may be rejected. Events from Amazon Kinesis streams and Amazon DynamoDB streams are retried until the Lambda function succeeds or the data expires. Kinesis and DynamoDB Streams retain data for 24 hours.

I had a similar issue with a lambda cron job function. I needed to send a request to a service/api that runs for a couple of seconds before it can return the first byte/response (no response processing needed), so my fix was like the following:

exports.handler = (event, context, callback) => {
// TODO implement

var https = require("https");
token = "xxxxxxxx";

var options = {
    host: "api.xxxxx.com",
    path: "/manage/cronjob/video",
    method: "GET",
    headers: {
        "Content-Type": "application/json",
        "Authorization": "Bearer "+token
    }
};

var req = https.request(options);
req.write("");
req.end();

//add timeout for context.done()
setTimeout(function(){
    context.done();
    callback(null, 'Hello from Lambda');
},1000); //This timeout should be lower than the lambda's timeout };

In this is example, we have an explicit callback to force the lambda exit, before the function gets a timeout error & triggers a retry for another 2 times

Hope it helps