AWS FinOps-101 (Reducing Costs for AWS S3 Bucket using AWS S3 Bucket Keys for Encryption)

Reducing Costs for AWS S3 Bucket using AWS S3 Bucket Keys   

Amazon Web Services (AWS) provides a range of cloud-based storage solutions, with Amazon S3 (Simple Storage Service) being one of the most popular and widely used. AWS S3 is known for its durability, scalability, and cost-effectiveness in managing large amounts of data. However, as organizations scale their storage needs, managing encryption and associated costs becomes an important factor. 

One of the key features introduced to help reduce encryption costs is AWS S3 Bucket Keys. The AWS S3 Bucket Keys help optimize the encryption process and reduce the associated costs, especially when using Server-Side Encryption with AWS Key Management Service (SSE-KMS). 

What Are S3 Bucket Keys? 

In Amazon S3, data at rest can be encrypted using Server-Side Encryption (SSE), which comes in three types: 

1. SSE-S3: SSE with S3 managed keys. 

2. SSE-KMS: SSE with AWS Key Management Service (KMS)-managed keys. 

3. SSE-C: SSE with Customer-managed keys. 

While SSE-S3 uses keys managed by AWS S3 itself, SSE-KMS provides more control by using keys managed through AWS KMS. However, using SSE-KMS comes at a cost. Each object in S3 encrypted with SSE-KMS has its own encryption key, and every request to read, write, or modify the encrypted object generates an API call to AWS KMS. These calls come with additional charges, which can add up significantly, especially when handling a large number of objects. 

S3 Bucket Keys are a way to streamline this process and reduce the number of KMS API calls. When you enable S3 Bucket Keys, AWS uses a single bucket-level key to encrypt multiple objects within the bucket instead of generating individual keys for each object. This reduces the number of KMS API calls required, cutting down on KMS charges. 

How do S3 Bucket Keys Work? 

The key idea behind S3 Bucket Keys is to simplify and centralize the encryption process. Here’s a step-by-step explanation of how this works: 

1. Object Encryption with SSE-KMS: 

Normally, when an object is uploaded to S3 with SSE-KMS encryption, each object is encrypted with a unique key managed by AWS KMS. This means each time an encrypted object is accessed (for a PUT, GET, COPY, or DELETE operation), AWS KMS must be called to manage that object’s encryption key. Each KMS API call incurs a small fee. 

2. Bucket-Level Key Management: 

When you enable S3 Bucket Keys, AWS uses a single encryption key for the entire bucket. This bucket-level key is then used to encrypt all objects within that bucket, drastically reducing the need for AWS KMS to generate unique keys for each individual object. Instead, the same encryption key is applied across the entire bucket, reducing the number of KMS operations needed. 

3. Single KMS Call for Multiple Objects: 

With S3 Bucket Keys, AWS only needs to make one call to KMS to obtain the encryption key for the entire bucket. This single KMS call reduces the overhead of multiple calls for every object stored or accessed in the bucket. The KMS call is made during the bucket's setup and remains the same for all objects in the bucket. 

4. Efficiency and Cost Savings: 

By reducing the number of KMS API calls, S3 Bucket Keys help lower the overall cost of using SSE-KMS encryption. You still get the added security benefits of using SSE-KMS but at a reduced cost since you're not paying for each individual API call related to the encryption of every object. 

Cost Savings with S3 Bucket Keys 

The most obvious benefit of S3 Bucket Keys is cost reduction. Here’s how they help you save money: 

Reduced API Call Charges: When using SSE-KMS without Bucket Keys, every object upload, retrieval, or modification triggers a call to KMS. For large volumes of objects, this can lead to substantial charges. With S3 Bucket Keys, you minimize these KMS API calls to just one per bucket, regardless of how many objects are stored. This reduces the number of calls to KMS and ultimately lowers the cost. 

Cost-Efficient for Large-Scale Operations: If you store millions or billions of objects, the savings can be significant. Instead of incurring KMS charges for every operation on each object, you only incur charges for a single key used for the entire bucket. This can result in savings in the range of thousands of dollars per month for large storage volumes. 

Better Cost Management for Encryption: Encryption management becomes more predictable and easier to track with S3 Bucket Keys, as you only need to worry about a single KMS key for the bucket, rather than tracking multiple keys for each individual object. 

How to Enable S3 Bucket Keys? 

Setting up S3 Bucket Keys is simple and can be done through the AWS Management Console or the AWS SDK. Here’s how you can enable it: 

1. Select SSE-KMS Encryption: 

During the process of setting up your S3 bucket or when uploading objects to the bucket, choose SSE-KMS as the encryption method. 

2. Enable S3 Bucket Keys: 

In the encryption settings, enable the option for S3 Bucket Keys. This ensures that all objects uploaded to the bucket will use the same encryption key and minimizes the number of KMS API calls. 

3. Automatic Management: 

Once enabled, AWS automatically handles the encryption using the bucket-level key. You don’t have to manually specify encryption keys for each object. 

4. Accessing Objects: 

When you retrieve or modify objects within the bucket, AWS uses the same bucket key, reducing the need for individual KMS calls. 

5. Performance Benefits:  

In addition to cost savings, S3 Bucket Keys can improve performance. By reducing the number of KMS calls, AWS can handle encryption and decryption more quickly, leading to faster data retrieval and better overall system performance. This is particularly beneficial when handling large datasets or frequently accessed objects, as it minimizes potential delays associated with encryption and decryption operations. 

AWS S3 Bucket Keys are a valuable feature for businesses that need to encrypt large volumes of data using SSE-KMS but want to reduce the associated costs. By allowing multiple objects to share a single encryption key at the bucket level, S3 Bucket Keys minimize the number of KMS API calls required for encryption operations. This leads to significant cost savings and improved performance for high-scale data storage use cases. 

For organizations looking to optimize their cloud storage costs while maintaining high security, enabling S3 Bucket Keys is a smart choice. It not only reduces your encryption costs but also simplifies key management, making it easier to manage your data securely and cost-effectively.