AWS Lambda has three invocation types — synchronous, asynchronous, and poll-based — and understanding the difference can save you from some tricky production surprises. With synchronous, your caller waits. With asynchronous, it fires and forgets. With poll-based, AWS does the polling for you.

This is the first post in my series on not-so-obvious AWS Lambda things. Read on for concrete examples of each invocation type, including boto3 code snippets and a poll-based gotcha worth knowing before you hit it in prod.