Serverless URL Shortener using AWS S3

This is an extremely simple serverless url shortener that relies on S3's ability to add a forwarding URL to objects.

https://docs.aws.amazon.com/AmazonS3/latest/userguide/how-to-page-redirect.html#redirect-requests-object-metadata

How to Use

Send a POST request to the lambda URL containing the following JSON:

{ "url": "https://very-long-url-to.be-shortened.com" }

The service will respond with the following JSON:

{ "key": "ka2jlk35", "url": "https://short.com/ka2jlk35" }

How to Setup

1. Register a custom domain with your preferred registrar.

2. Create an S3 bucket which has precisely the same name as your domain name.

   • Be sure to un-check all of the "private-only" boxes, as this will be a public bucket.

3. In bucket properties, turn on "Static website hosting"

   • Hosting type: Host a static website
   • Index document: index.html

4. In bucket permissions, update the policy to allow public reads:

   {
       "Version": "2012-10-17",
       "Statement": [
           {
               "Sid": "PublicReadGetObject",
               "Effect": "Allow",
               "Principal": "*",
               "Action": "s3:GetObject",
               "Resource": "arn:aws:s3:::BUCKET_NAME/*"
           }
       ]
   }

   • Replace "BUCKET_NAME" in the above with your bucket/domain

5. Create a new Lambda function

   • Runtime: Node.js
   • Execution role: Create a new role with basic Lambda permissions
   • Advanced Settings - Check Enable function URL

6. Build and upload this lambda function code

   • Check-out this repository from GIT
   • Run npm install
   • Open index.js and replace constants (eg. your bucket name)
   • Compress entire folder (including node_modules) into a .zip
   • Click "Upload from" > .zip in the Lambda UI

7. Update lambda permissions to access S3 bucket

   • Open IAM Roles, find the newly created role for this lambda
   • Add permissions > Create inline policy, with following:

     {
         "Version": "2012-10-17",
         "Statement": [
             {
                 "Sid": "ListObjectsInBucket",
                 "Effect": "Allow",
                 "Action": [
                     "s3:ListBucket"
                 ],
                 "Resource": [
                     "arn:aws:s3:::BUCKET_NAME"
                 ]
             },
             {
                 "Sid": "AllObjectActions",
                 "Effect": "Allow",
                 "Action": "s3:*Object",
                 "Resource": [
                     "arn:aws:s3:::BUCKET_NAME/*"
                 ]
             }
         ]
     }

   • Replace "BUCKET_NAME" in the above with your bucket/domain name.

8. (OPTIONAL) Configure an object for responding to requests at the root.

   • You can use the S3 UI to upload a index.html file. This can be a static website, or you can forward it to another domain.
   • To forward requests to index.html elsewhere, open the object properties, Edit Metadata, Add new System defined metadata, Key: x-amz-website-redirect-location