Thread by @tpschmidt_

📚 AWS 1x1: 𝗪𝗵𝗮𝘁 𝗮𝗿𝗲 𝗟𝗮𝗺𝗯𝗱𝗮 𝘁𝗿𝗶𝗴𝗴𝗲𝗿𝘀?

For a function to execute, an event must occur.
Most know about API Gateway for REST services as an event source.

But a lot more AWS resources can trigger your Lambda ↓

Almost anything that happens within your AWS account is an event.

• writing a record to DynamoDB
• uploading a file to S3
• queuing a message in SQS
• a viewer request to your CloudFront distribution

All of those events can be used to trigger a Lambda function.

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There are two different kinds of invocation types: 𝘀𝘆𝗻𝗰𝗵𝗿𝗼𝗻𝗼𝘂𝘀 & 𝗮𝘀𝘆𝗻𝗰𝗵𝗿𝗼𝗻𝗼𝘂𝘀

Synchronous event sources need to wait for your Lambda function to return a response.
Asynchronous don't.

If invoking functions via the SDK, this can be specified!

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Let's have a look at a sample invocation:

𝗮𝘄𝘀 𝗹𝗮𝗺𝗯𝗱𝗮 𝗶𝗻𝘃𝗼𝗸𝗲 \
—𝗳𝘂𝗻𝗰𝘁𝗶𝗼𝗻-𝗻𝗮𝗺𝗲 𝗺𝘆-𝗳𝘂𝗻𝗰𝘁𝗶𝗼𝗻 \
—𝗶𝗻𝘃𝗼𝗰𝗮𝘁𝗶𝗼𝗻-𝘁𝘆𝗽𝗲 𝗥𝗲𝗾𝘂𝗲𝘀𝘁𝗥𝗲𝘀𝗽𝗼𝗻𝘀𝗲

RequestResponse is the default, providing synchronous calls.

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If you're passing 𝗘𝘃𝗲𝗻𝘁, the invocation will be triggered asynchronously.

If used in another function, the code execution will just continue after submitting the call.

💡 If your function returns an error, AWS will automatically 𝗿𝗲𝘁𝗿𝘆 the invoke 𝘁𝘄𝗶𝗰𝗲

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Let's have a more detailed look at the most common Lambda triggers: 𝗔𝗣𝗜 𝗚𝗮𝘁𝗲𝘄𝗮𝘆𝘀, 𝗦𝟯, and 𝗗𝘆𝗻𝗮𝗺𝗼𝗗𝗕 𝘁𝗮𝗯𝗹𝗲 𝘀𝘁𝗿𝗲𝗮𝗺𝘀.

They can be found in a lot of widely used architectural patterns.

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𝗔𝗣𝗜 𝗚𝗮𝘁𝗲𝘄𝗮𝘆 𝗧𝗿𝗶𝗴𝗴𝗲𝗿

Invocations by API Gateway are synchronous ones, waiting for your Lambda to return a response it can send back to the requesting client.
You need to explicitly map which invocation paths you want to map to with function.

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𝗦𝟯 𝗧𝗿𝗶𝗴𝗴𝗲𝗿

Events occur when the content in an S3 bucket is modified, e.g. by creating, removing, or updating a file.
When defining an event, you’re able to specify what sort of action will trigger the lambda function and which paths you want to include

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𝗗𝘆𝗻𝗮𝗺𝗼𝗗𝗕 𝗦𝘁𝗿𝗲𝗮𝗺 𝗧𝗿𝗶𝗴𝗴𝗲𝗿𝘀

If streams are enabled for a table, all changes are pushed into such a stream if there were changes made to an item or a new item was inserted.
Think of it like a line or a queue through which the data flows.

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If there's data inside that stream, a Lambda function will be triggered with related data.
The stream data can be 𝗮𝗴𝗴𝗿𝗲𝗴𝗮𝘁𝗲𝗱, meaning that a single Lambda invocation can contain 𝗺𝘂𝗹𝘁𝗶𝗽𝗹𝗲 change records.

Invocations are asynchronous like at S3.

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There are a lot of other 𝘀𝘆𝗻𝗰𝗵𝗿𝗼𝗻𝗼𝘂𝘀 𝗲𝘃𝗲𝗻𝘁 𝘀𝗼𝘂𝗿𝗰𝗲𝘀...

• Elastic Load Balancing (ALB)
• Cognito
• Alexa
• API Gateway
• CloudFront
• Kinesis Data Firehose
• Simple Storage Service Batch
• Amazon Connect
• Amazon Lex

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... and also 𝗮𝘀𝘆𝗻𝗰𝗵𝗿𝗼𝗻𝗼𝘂𝘀 ones!

• CodePipeline
• S3
• SNS
• SES
• CloudFormation
• CloudWatch Logs
• CloudWatch/EventBridge Events
• CodeCommit
• AWS Config
• AWS IoT
• AWS IoT Events

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If you're more interested in Lambda triggers and what architectural patterns you can build with them, have a look at the 𝗖𝗼𝗺𝗽𝗹𝗲𝘁𝗲 𝗚𝘂𝗶𝗱𝗲 𝘁𝗼 𝗟𝗮𝗺𝗯𝗱𝗮 𝗧𝗿𝗶𝗴𝗴𝗲𝗿𝘀 𝗮𝗻𝗱 𝗗𝗲𝘀𝗶𝗴𝗻 𝗣𝗮𝘁𝘁𝗲𝗿𝗻𝘀 by @thedashbird 🏗

dashbird.io/blog/complete-…

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Thank you for reading!
I hope you learned something new 🙌

As usual: I'm happy about a ♻️ or ♥️ of the initial post.

... and drop me a follow if you're interested in regular cloud content! 🌤