SQS as an event trigger for Lambda

Question

I am trying to implement a service within a serverless architecture that will take "Orders" that are basically JSON objects, and every X number of orders, trigger a Lambda function to process those orders. I have read a fair bit about Amazon SQS as an option for something like this, but want to get confirmation that this is the right approach.

Can I use SQS to subscribe to an SNS feed that publishes orders, and then have a Lambda poll that queue to batch process orders that come in?

Thanks in advance.

Answer 1

I did some experimentation and found that:

• If multiple messages are sent to Amazon SQS with SendMessageBatch()
• Then those messages will be passed to a single AWS Lambda function as multiple entries in the Records parameter
• But only up to the maximum number of records set by the Batch Size in the Lambda trigger

Therefore, if your ordering system can send the messages to SQS as a batch, then the Lambda function will process them as a batch (up to the Batch Size). However, this would require you to 'buffer' the messages in the ordering system before sending them to Lambda, which has the potential for information loss if something goes wrong.

It is typically better to process the orders immediately unless there is a specific reason why you wish to use a batch.

Inserting Amazon SNS can be useful if you wish to "fan-out" the orders to multiple systems, but isn't necessary if you have only one destination for the messages.