DEV Community: Success Enin

Configuring Lambda for the Serverless Application

Success Enin — Fri, 03 Oct 2025 12:13:25 +0000

As a continuation to the series, this post covers everything you need to know about configuring Lambda and Lambda Functions

Read this post to learn how to configure Lambda:Post

Note: The Lambda function is written in Python

See repo for code: Repo

Replace only the DynamoDB table name, and partition key name in the Phyton code with your own.How to get a table name?.

Navigate to the Lambda console, select the function you created, click on code then paste your edited code and then deploy.

On that same function screen, click on Add Trigger, select API Gateway for trigger source, mark "Use Existing API" and then select the API created preciously. Finally click Add.

Triggers

Triggers are what invokes a Lambda Function to run. An invocation can happen in many scenarios e.g when you upload a file on Amazon S3, or When a request is made through your API endpoint.

What To Watch Out For

Make sure:

Your API Endpoint is included in the HTML code
Your Trigger is set to the correct API
The DynamoDb name and Partition key are spelt correctly

Conclusion

Right now you should have a frontend that invokes your Lambda Function through an API Gateway endpoint, and a Lambda Function then stores reservation details on the backend in DynamoDB.

Creating an AWS DynamoDB

Success Enin — Fri, 03 Oct 2025 11:47:01 +0000

1. Go to the AWS Management Console.
2. Navigate to the DynamoDB console, then click Create Table.
3. Input a table name of your choice and a partition key name of your choice (e.g "res").
4. You can then choose the default settings or customize your own depending on your use case.
Click on create table and you are good to go.

Configuring Amazon S3 Bucket and Object for the Serverless Application

Success Enin — Fri, 03 Oct 2025 11:02:58 +0000

To configure an Amazon S3 bucket accurately read this post: How to configure an S3 bucket

See repo for web app code: Repo

Remember to edit the API endpoint in the code provided

Endpoint must be your own unique API endpoint gotten from deploying the API Gateway
"Prod" in my endpoint is the stage name
"Res" is the resource name.

In the newly created S3 bucket, upload the edited html file.

Deploying API On AWS API Gateway

Success Enin — Fri, 03 Oct 2025 10:34:09 +0000

This post is the first of a series on deploying a server less infrastructure on AWS cloud.

What is an API Gateway?

An API Gateway is a managed service that sits between frontend clients and backend services, acting as an entry point for API requests.

How To Provision API Gateway

For this series the serverless application I will be building is a restaurant reservation web app, hosted on Amazon S3 which collects clients reservation information through the frontend, passes it through the gateway endpoint which triggers a Lambda function to process the data and store it in AWS DynamoDB. For this use case my gateway endpoint will be a REST API with a POST method. To provision this,

First you head to your AWS Management Console, navigate to the API console, then you click on "Create API". In the choose an API type page click on build on the REST API option, give the API a name, API endpoint type will be set to regional, IP address type will be IPv4 then create the api

After creating the API you must then configure it to your use case, for my use case I want an API that can carry out a POST request to my DynamoDB table by triggering Lambda. As a result you must create a resource, the path should be set to "/", resource name should be set to your choice of name and remember to enable CORS since our request will be coming from another frontend site hosted on Amazon S3. Hosting a static website on S3.

For the next step will be selecting a method type, but first we need a Lambda function (Creating a Lambda Function).

Head to the create method page, set the Method Type to "POST", integration type to Lambda Function, then select the Lambda Function provisioned earlier, and create the method.

Next you must deploy the API, while deploying you would be prompted for a stage name, give a name of your choice. Navigate to the stage you just created and copy the invoke url.

Creating A Lambda Function in AWS

Success Enin — Fri, 03 Oct 2025 09:47:47 +0000

Step-by-step guide on creating a Lambda Function

First you head to the AWS management console then navigate to Lambda console, Click on create function
In the create function page, select author from scratch, give your function a name unique to the AWS region you're in, select a runtime (e.g Node.js, Python, Ruby, Java), Architecture should be left at default, Leave execution role at default, Then create function.

Configuring Connection From On-Premises Server To The Cloud

Success Enin — Wed, 24 Sep 2025 12:32:25 +0000

While some companies move 100% of their infrastructure to the cloud some prefer a hybrid system which combines on-premises infrastructure with cloud services.
The two ways to form a connection from on-premises server to AWS clouds is through a site-site connection and direct connect connection. In this post I would be explaining in easy to understand terms how to form this connection.

Site-Site VPN

This is a connection from an on-premises server to AWS through the internet.
But not so easy there are some cloud services and on-premises hardware you need to provision before this connection is formed. How does this connection happen?

First you create a virtual private network in your VPC, as a result you are provided with a VPN endpoint which lives in the virtual private gateway. This VPN endpoint is then provided to your on-premises device (router) that support IPsec (Internet Protocol Security), Your router and VPN endpoint then uses IPsec to authenticate each-other.

Once the encryption is established a secure tunnel is created over the internet which will facilitate the connection between your on-premises network and VPC. After this is done, your on-premises network can now see AWS subnets, and AWS can see your on-premises subnets.

Direct Connect (DX)

The connection does not have to go through the public Internet instead it goes through a private fibre link. This private fibre link is gotten by contacting a telecom provider who then provides a dedicated link from your on-premises network to AWS direct connect location. From these locations your connection then enters a logical lane through a virtual interface which is tied your VPC through a virtual private gateway or transit gateway (this can enable connection to more than one VPC)

Now your servers can interact and they do not need to go through the internet, they just utilize these fibre cable connections.

Pros and Cons

Site-Site VPN connections are fast to set up, cheap, and they are perfect for small or medium traffic, But they depend on the public internet which may not always be reliable and increase latency.
Direct Connect connections are reliable and cheaper since AWS gives discounts if you move a lot of data, But are more expensive upfront and takes lots of time to set up.

Conclusion

Chooses between the two connection models really boils down to your use case, availability, the size of your organization, safety and compliance laws and finances.

Connecting On-Premises Network To The Cloud

Success Enin — Wed, 24 Sep 2025 11:28:14 +0000

You've got your company's network and you need it to securely talk to your VPC infrastructure on the AWS cloud as if they are a single network. There are two ways to securely do this:

Site-Site VPN (Virtual Private Network)
Direct Connect (DX)

Subnetting in AWS

Success Enin — Tue, 23 Sep 2025 18:53:55 +0000

This post covers the fundamentals of subnetting in the AWS console and how to properly subnet your networks.

What is Subnetting

In AWS, subnetting is dividing your VPC (Virtual Private Cloud)network into smaller networks called subnets.

What is a Subnet

A subnet is a network within a network.

CIDR Block

To properly divide your VPC CIDR block into working subnets you must first understand what CIDR blocks are made up of.

CIDR blocks are made up of five numbers, the first four being the routing prefix and the last number with usually has a "/" before the number and it is called a netmask e.g (10.0.0.0/24). Each octet in the routing prefix separated by dots have 8 bit.

The net mask tells you how many of the 32 bit routing prefix must be fixed or allocated for the network identifier.

So in a /24 net mask the first three octets are fixed and the fourth one can change to give you a group of IP addresses that are consecutive to one another.

Calculating the number of available IP address in a CIDR block

For this example we will be using an IP address with a /24 net mask. Take the IP dress 10.0.0.0/24 the simple way to calculate the number of available IP addresses here would be
host bits = 32 - 24 = 8
total IPs = 2^8 = 256

Further subnetting of our VPC into a /27 network would mean we have 32 subnets to allocate per subnet which means we can have up to 8 subnets in the VPC.

Subnetting a /24 network

To make sure your subnets do not have overlapping IPs you can configure your IP ranges like this: The fist subnet can have an IP range of 10.0.0.0/27 - 10.0.0.32/27, the second subnet should then have IPs ranging from 10.0.0.33/27 - 10.0.0.64/27 the third subnet follows with would range from 10.0.0.65/27 - 10.0.0.96/27 etc. Each subnet in the /27 network start where the previous one ended.

Conclusion

Subnetting is the most crucial part of a cloud infrastructure and knowing how to subnet a network is a crucial skill for a cloud engineer. Learning and writing about this today has deepened my knowledge of subnets and I hope reading this post does the same for you too.

Hosting a static webpage using Amazon Simple Storage Service (S3)

Success Enin — Mon, 22 Sep 2025 17:33:31 +0000

This publications is all about showing you how to showcase your static webpage on the web using AWS services and in this case using Amazon Simple Storage Services (S3). I've also documented all the mistakes I made while deploying this project in the hope that you would read it and not make the same mistake or better still make better mistakes of your own.

Overview

The project shows you how to properly and easily host your static web page using S3 service on AWS.

What is S3?

Amazon S3 is AWS's own block storage service, that automatically replicates any data stored on it to three availability zone in the same region.

What is a Static Website?

A static website is one made up of fixed files e.g. HTML, Javascript and are delivered to the browser as they are. A static website has no server-side code.

AWS Setup

AWS Account
Create an S3 bucket.

Configuring the S3 Buckets

While creating the S3 bucket, you will be required to configure some setting. Below I will go through the steps of configuration and how to properly select your favored options.

Select the general purpose bucket type.
Name the bucket: In AWS the bucket name must be unique.
Disable ACL
Disable the block public access option
Enable bucket versioning
Select "Server-side encryption with Amazon S3 managed keys (SSE-S3)" in the encryption option
Disable bucket key
Navigate to the "Create Bucket" button and click it.

Configuring the bucket

Provisioning the S3 is just the first part of hosting your static website on S3. The next steps will show you how to properly set your S3 bucket to provision effectively.

Click on upload and upload the necessary files (e.g Html, CSS)
Navigate your way into the already created bucket, then click properties.
Scroll all the way down and enable static website hosting. while enabling static website on the index document, specify the default page of the website (e.g index.html), then click on "Save changes" button.
Go back to your bucket directory then click on permission. Look for the bucket policy and click on edit: on the notepad input the below policy to allow access to objects stored in the bucket (e.g html file)- , then click on "Save changes" button.
Now go back to the bucket directory, click on the permissions tab, scroll all the way down and click on the website endpoint link, your webpage should be ready now.

Mistakes

Mistake 1
When I was specifying the default page of the website as seen in step 3 of the bucket configuration steps, I named it in this format "folder-name/file-name.html" because I had uploaded the whole folder to S3 and I had to properly link the index document but this kind of linking will give off this error in the AWS Console:

This is the correct way to name your directory in the AWS Console:

Mistake 2
While trying to access the webpage I was denied access because I had not provided the bucket policy that would give access to the objects in the S3 bucket as seen in step 4 of the bucket configuration steps.

Conclusion

While setting up the S3 bucket to host the webpage effectively I made a couple mistakes, these mistakes also forced me to understand how bucket policies and naming in AWS works.