# Synchronous & Asynchronous Lambda
* Several AWS services, such as S3 and SNS, **invoke functions asynchronously to process events**.
* When you invoke a function asynchronously, you don't wait for a response from the function code.
* You hand off the event to Lambda and Lambda handles the rest.
* You can configure how Lambda handles errors, and can send invocation records to a downstream resource to chain together components of your application.
* **Lambda supports the synchronous and asynchronous invocation** of a Lambda function.
* You can **control the invocation type only when you invoke a Lambda function**.
* **When you use an AWS service as a trigger, the invocation type is predetermined for each service**.
* You have **no control over the invocation type that these event sources use when they invoke your Lambda function**.
* **For short-term, Lambda is a very cost-effective choice**.
* You can **use a Lambda function to process messages in an SQS queue**.
* **Lambda event source mappings support standard queues and FIFO queues**.
* **With SQS, you can offload tasks from one component of your application** by sending them to a queue and **processing them asynchronously**.
* **Kinesis Data Streams is a real-time data streaming service** that **requires the provisioning of shards**.
* **With SQS only pay for what you use**, so it is a cheaper alternative.
* **If you don't need real-time processing, replacing Kinesis Data Streams with SQS would lower costs**.