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Okay, so let's talk about a serverless hosted website,

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maybe called myblog.com.

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So our website should scale globally,

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and we rarely write blogs, we often read blogs.

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So our blogs is seen by

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hundreds of thousands of people online,

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and we rarely add blogs, maybe one a day, one a week,

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but most of the time these blogs are being read.

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And so most of my website is going to be purely static files

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and maybe a little bit of my website

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is going to be a dynamic REST API.

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I want to implement caching where possible

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to relieve save cost and save latency,

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and have a great user experience.

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And any new users that subscribes to my website, to my blog,

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I really want them to receive a warm welcome Email,

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and this should be serverless.

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And any photo uploaded to the blog,

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I also want to have a thumbnail being generated,

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also serverless because I really like serverless.

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So how do we implement all these requirements?

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Number one, we want to serve content,

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it's static and it's global.

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So if you remember, we have our client,

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and our static content may be stored in Amazon S3.

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So how do we expose that bucket?

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Remember the Amazon S3 bucket is in specific region.

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How do we expose this globally?

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Well we can use Amazon CloudFront,

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and Amazon CloudFront is a global distribution CDN,

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and so basically our clients is going to

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interact with edge locations on Amazon CloudFront,

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and it's going to cage data coming straight from Amazon S3.

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Okay super easy, we've seen CloudFront,

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we've seen S3, as a classic architecture.

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Now how do we do this securely?

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Now that's a very common question as well,

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so we have the client it's interacting with CloudFront,

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and it's a global distribution still,

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but now, we're going to use OAI,

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or an Origin Access Identity from CloudFront to S3.

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Basically saying, okay, we're going to add a bucket policy,

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and the bucket policy on S3 will say,

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you only authorize the OAI, so CloudFront, to read,

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the rest cannot.

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And so that secures it, because now our clients

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they cannot go directly to the S3 bucket to get the content.

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They have to go through CloudFront,

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and in this way we've secured our infrastructure.

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Okay, so now we have this, and this is really good.

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How do we add a public serverless REST API?

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Well for this we'll have a REST HTTPS cloud talking

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to Amazon API Gateway, invoking a Lambda function,

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maybe querying and reading from DynamoDB,

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and because we have so many reads,

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maybe DAX is a great caching layer we could use, okay?

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So far very easy.

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If we're going global,

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maybe we could be leveraging DynamoDB global databases

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to reduce the latencies in part of the world.

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That also could be a really good way

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of maybe speeding up our infrastructure

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and our architecture.

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Okay so this is fine, we have everything we need.

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Now let's talk about the user welcome email flow.

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Well here, remember when a user subscribes

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I want them to be having an email saying,

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hello, how are you?

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So for this, maybe in DynamoDB

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we want to enable streams of changes,

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so we'll have DynamoDB stream being created,

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and that DynamoDB stream will invoke a Lambda function.

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That Lambda function is going to be very special,

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it's going to have an IAM role,

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which allows us to use Amazon SES.

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So we haven't seen what Amazon SES is,

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but it's really simple.

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It's called Amazon Simple Email Service, so SES,

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and it basically allows us to send emails.

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So here our Amazon Lambda function can use the AWS SDK

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to send emails from Amazon SES, and here we go,

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we have a basically serverless user welcome email flow,

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and really simple, no infrastructure to manage,

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it just works and scales really really well.

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Okay, so now we said, okay if users upload images

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we want thumbnails to be created, so our client,

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is going to maybe upload to our S3 bucket directly,

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or maybe we again have an OAI in a CloudFront distribution.

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In which case our client will upload photos to CloudFront,

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and CloudFront will forward them onto the Amazon S3 bucket,

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and this is called S3 transfer acceleration.

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So either directly to S3, or using transfer acceleration,

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and then we will do is that whenever a file is added to S3

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it's going to trigger a Lambda function,

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so Lambda can be triggered by S3,

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and Lambda will be creating a thumbnail

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and putting that thumbnail into an S3 bucket,

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could be a different bucket for example.

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And just to show you it's possible,

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Amazon S3 also has triggers to SQS and SNS.

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Now this is optional,

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and from SQS SNS you can do whatever you want,

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but it's just to show you that your very free

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into how you want things to work,

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and so Amazon S3 can invoke either Lambda, SQS, or SNS,

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and you're really free to think about your

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solution architecture and how to make things serverless

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and easy for you on your end.

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So this is quite a complete architecture we've just done,

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but it's all serverless, it's all scaling globally,

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and I think that's what matters most.

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So we've seen static content being distributed

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using CloudFront with S3.

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We've seen the REST API that was serverless,

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we didn't need Cognito this time

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because it was a public REST API,

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and we leveraged a global DynamoDB table

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to serve the data globally.

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We could have used also Aurora Global Database,

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but in this case it wouldn't have been such serverless,

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it would have been provisioned Aurora.

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We could also enable DynamoDB streams,

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basically these streams should tell us about changes

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to our user tables and then trigger a Lambda function,

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and that Lambda function had a IAM role attached to it,

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so it could use SES or Simple Email Service,

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and this was just to send emails in a serverless way.

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And S3 we've seen that it could trigger

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SQS, SNS, Lambda to be notify of events.

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So quite a lot of learnings, all these things we know,

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but it's now, I think, really nice

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to see all these things working together,

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and how we can create some really cool applications

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using all the concepts we know.

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So I hope you liked it,

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and I will see you in the next lecture.