AWS S3 Versioning

S3 Versioning

  • S3 Versioning helps to keep multiple variants of an object in the same bucket and can be used to preserve, retrieve, and restore every version of every object stored in the S3 bucket.
  • S3 Object Versioning can be used to protect from unintended overwrites and accidental deletions
  • As Versioning maintains multiple copies of the same objects as a whole and charges accrue for multiple versions for e.g. for a 1GB file with 5 copies with minor differences would consume 5GB of S3 storage space and you would be charged for the same.
  • Buckets can be in one of the three states
    • Unversioned (the default)
    • Versioning-enabled
    • Versioning-suspended
  • S3 Object Versioning is not enabled by default and has to be explicitly enabled for each bucket.
  • Versioning once enabled, cannot be disabled and can only be suspended
  • Versioning enabled on a bucket applies to all the objects within the bucket
  • Permissions are set at the version level. Each version has its own object owner; an AWS account that creates the object version is the owner. So, you can set different permissions for different versions of the same object.
  • Irrespective of the Versioning, each object in the bucket has a version.
    • For Non Versioned bucket, the version ID for each object is null
    • For Versioned buckets, a unique version ID is assigned to each object
  • With Versioning, version ID forms a key element to define the uniqueness of an object within a bucket along with the bucket name and object key

Object Retrieval

  • For Non Versioned bucket
    • An Object retrieval always returns the only object available.
  • For Versioned bucket
    • An object retrieval returns the Current latest object.
    • Non-Current objects can be retrieved by specifying the version ID.

Object Addition

  • For Non Versioned bucket
    • If an object with the same key is uploaded again it overwrites the object
  • For Versioned bucket
    • If an object with the same key is uploaded, the newly uploaded object becomes the current version and the previous object becomes the non-current version.
    • A non-current versioned object can be retrieved and restored hence protecting against accidental overwrites

Object Deletion

  • For Non Versioned bucket
    • An object is permanently deleted and cannot be recovered
  • For the Versioned bucket,
    • All versions remain in the bucket and Amazon inserts a delete marker which becomes the Current version
    • A non-current versioned object can be retrieved and restored hence protecting against accidental overwrites
    • If an Object with a specific version ID is deleted, a permanent deletion happens and the object cannot be recovered

Delete marker

  • Delete Marker object does not have any data or ACL associated with it, just the key and the version ID
  • An object retrieval on a bucket with a delete marker as the Current version would return a 404
  • Only a DELETE operation is allowed on the Delete Marker object
  • If the Delete marker object is deleted by specifying its version ID, the previous non-current version object becomes the current version object
  • If a DELETE request is fired on an object with Delete Marker as the current version, the Delete marker object is not deleted but a Delete Marker is added again

S3 Versioning - Delete Operation

Restoring Previous Versions

  • Copy a previous version of the object into the same bucket. The copied object becomes the current version of that object and all object versions are preserved – Recommended as it keeps all the versions.
  • Permanently delete the current version of the object. When you delete the current object version, you, in effect, turn the previous version into the current version of that object.

Versioning Suspended Bucket

  • Versioning can be suspended to stop accruing new versions of the same object in a bucket.
  • Existing objects in the bucket do not change and only future requests behavior changes.
  • An object with version ID null is added for each new object addition.
  • For each object addition with the same key name, the object with the version ID null is overwritten.
  • An object retrieval request will always return the current version of the object.
  • A DELETE request on the bucket would permanently delete the version ID null object and inserts a Delete Marker
  • A DELETE request does not delete anything if the bucket does not have an object with version ID null
  • A DELETE request can still be fired with a specific version ID for any previous object with version IDs stored

MFA Delete

  • Additional security can be enabled by configuring a bucket to enable MFA (Multi-Factor Authentication) for the deletion of objects.
  • MFA Delete enabled, requires additional authentication for operations
    • Changing the versioning state of the bucket
    • Permanently deleting an object version
  • MFA Delete can be enabled on a bucket to ensure that data in the bucket cannot be accidentally deleted
  • While the bucket owner, the AWS account that created the bucket (root account), and all authorized IAM users can enable versioning, but only the bucket owner (root account) can enable MFA Delete.
  • MFA Delete however does not prevent deletion or allow restoration.
  • MFA Delete cannot be enabled using the AWS Management Console. You must use the AWS Command Line Interface (AWS CLI) or the API.

AWS Certification Exam Practice Questions

  • Questions are collected from Internet and the answers are marked as per my knowledge and understanding (which might differ with yours).
  • AWS services are updated everyday and both the answers and questions might be outdated soon, so research accordingly.
  • AWS exam questions are not updated to keep up the pace with AWS updates, so even if the underlying feature has changed the question might not be updated
  • Open to further feedback, discussion and correction.
  1. Which set of Amazon S3 features helps to prevent and recover from accidental data loss?
    1. Object lifecycle and service access logging
    2. Object versioning and Multi-factor authentication
    3. Access controls and server-side encryption
    4. Website hosting and Amazon S3 policies
  2. You use S3 to store critical data for your company Several users within your group currently have full permissions to your S3 buckets. You need to come up with a solution that does not impact your users and also protect against the accidental deletion of objects. Which two options will address this issue? Choose 2 answers
    1. Enable versioning on your S3 Buckets
    2. Configure your S3 Buckets with MFA delete
    3. Create a Bucket policy and only allow read only permissions to all users at the bucket level
    4. Enable object life cycle policies and configure the data older than 3 months to be archived in Glacier
  3. To protect S3 data from both accidental deletion and accidental overwriting, you should
    1. enable S3 versioning on the bucket
    2. access S3 data using only signed URLs
    3. disable S3 delete using an IAM bucket policy
    4. enable S3 Reduced Redundancy Storage
    5. enable Multi-Factor Authentication (MFA) protected access
  4. A user has not enabled versioning on an S3 bucket. What will be the version ID of the object inside that bucket?
    1. 0
    2. There will be no version attached
    3. Null
    4. Blank
  5. A user is trying to find the state of an S3 bucket with respect to versioning. Which of the below mentioned states AWS will not return when queried?
    1. versioning-enabled
    2. versioning-suspended
    3. unversioned
    4. versioned


AWS S3 Versioning

AWS S3 Best Practices

S3 Best Practices


Multiple Concurrent PUTs/GETs

  • S3 scales to support very high request rates. If the request rate grows steadily, S3 automatically partitions the buckets as needed to support higher request rates.
  • S3 can achieve at least 3,500 PUT/COPY/POST/DELETE and 5,500 GET/HEAD requests per second per prefix in a bucket.
  • If the typical workload involves only occasional bursts of 100 requests per second and less than 800 requests per second, AWS scales and handle it.
  • If the typical workload involves a request rate for a bucket to more than 300 PUT/LIST/DELETE requests per second or more than 800 GET requests per second, it’s recommended to open a support case to prepare for the workload and avoid any temporary limits on your request rate.
  • S3 best practice guidelines can be applied only if you are routinely processing 100 or more requests per second
  • Workloads that include a mix of request types
    • If the request workload is typically a mix of GET, PUT, DELETE, or GET Bucket (list objects), choosing appropriate key names for the objects ensures better performance by providing low-latency access to the S3 index
    • This behavior is driven by how S3 stores key names.
      • S3 maintains an index of object key names in each AWS region.
      • Object keys are stored lexicographically (UTF-8 binary ordering) across multiple partitions in the index i.e. S3 stores key names in alphabetical order.
      • Object keys are stored in across multiple partitions in the index and the key name dictates which partition the key is stored in
      • Using a sequential prefix, such as timestamp or an alphabetical sequence, increases the likelihood that S3 will target a specific partition for a large number of keys, overwhelming the I/O capacity of the partition.
    • Introduce some randomness in the key name prefixes, the key names, and the I/O load, will be distributed across multiple index partitions.
    • It also ensures scalability regardless of the number of requests sent per second.

Transfer Acceleration

  • S3 Transfer Acceleration enables fast, easy, and secure transfers of files over long distances between the client and an S3 bucket.
  • Transfer Acceleration takes advantage of CloudFront’s globally distributed edge locations. As the data arrives at an edge location, data is routed to S3 over an optimized network path.

GET-intensive Workloads

  • CloudFront can be used for performance optimization and can help by
    • distributing content with low latency and high data transfer rate.
    • caching the content and thereby reducing the number of direct requests to S3
    • providing multiple endpoints (Edge locations) for data availability
    • available in two flavors as Web distribution or RTMP distribution
  • To fast data transport over long distances between a client and an S3 bucket, use S3 Transfer Acceleration. Transfer Acceleration uses the globally distributed edge locations in CloudFront to accelerate data transport over geographical distances

PUTs/GETs for Large Objects

  • AWS allows Parallelizing the PUTs/GETs request to improve the upload and download performance as well as the ability to recover in case it fails
  • For PUTs, Multipart upload can help improve the uploads by
    • performing multiple uploads at the same time and maximizing network bandwidth utilization
    • quick recovery from failures, as only the part that failed to upload, needs to be re-uploaded
    • ability to pause and resume uploads
    • begin an upload before the Object size is known
  • For GETs, the range HTTP header can help to improve the downloads by
    • allowing the object to be retrieved in parts instead of the whole object
    • quick recovery from failures, as only the part that failed to download needs to be retried.

List Operations

  • Object key names are stored lexicographically in S3 indexes, making it hard to sort and manipulate the contents of LIST
  • S3 maintains a single lexicographically sorted list of indexes
  • Build and maintain Secondary Index outside of S3 for e.g. DynamoDB or RDS to store, index and query objects metadata rather than performing operations on S3


  • Use Versioning
    • can be used to protect from unintended overwrites and deletions
    • allows the ability to retrieve and restore deleted objects or rollback to previous versions
  • Enable additional security by configuring a bucket to enable MFA (Multi-Factor Authentication) to delete
  • Versioning does not prevent Bucket deletion and must be backed up as if accidentally or maliciously deleted the data is lost
  • Use Same Region Replication or Cross Region replication feature to backup data to a different region
  • When using VPC with S3, use VPC S3 endpoints as
    • are horizontally scaled, redundant, and highly available VPC components
    • help establish a private connection between VPC and S3 and the traffic never leaves the Amazon network

Refer blog post @ S3 Security Best Practices


  • Optimize S3 storage cost by selecting an appropriate storage class for objects
  • Configure appropriate lifecycle management rules to move objects to different storage classes and expire them


  • Use Event Notifications to be notified for any put or delete request on the S3 objects
  • Use CloudTrail, which helps capture specific API calls made to S3 from the AWS account and delivers the log files to an S3 bucket
  • Use CloudWatch to monitor the Amazon S3 buckets, tracking metrics such as object counts and bytes stored, and configure appropriate actions

S3 Monitoring and Auditing Best Practices

Refer blog post @ S3 Monitoring and Auditing Best Practices

AWS Certification Exam Practice Questions

  • Questions are collected from Internet and the answers are marked as per my knowledge and understanding (which might differ with yours).
  • AWS services are updated everyday and both the answers and questions might be outdated soon, so research accordingly.
  • AWS exam questions are not updated to keep up the pace with AWS updates, so even if the underlying feature has changed the question might not be updated
  • Open to further feedback, discussion and correction.
  1. A media company produces new video files on-premises every day with a total size of around 100GB after compression. All files have a size of 1-2 GB and need to be uploaded to Amazon S3 every night in a fixed time window between 3am and 5am. Current upload takes almost 3 hours, although less than half of the available bandwidth is used. What step(s) would ensure that the file uploads are able to complete in the allotted time window?
    1. Increase your network bandwidth to provide faster throughput to S3
    2. Upload the files in parallel to S3 using multipart upload
    3. Pack all files into a single archive, upload it to S3, then extract the files in AWS
    4. Use AWS Import/Export to transfer the video files
  2. You are designing a web application that stores static assets in an Amazon Simple Storage Service (S3) bucket. You expect this bucket to immediately receive over 150 PUT requests per second. What should you do to ensure optimal performance?
    1. Use multi-part upload.
    2. Add a random prefix to the key names.
    3. Amazon S3 will automatically manage performance at this scale.
    4. Use a predictable naming scheme, such as sequential numbers or date time sequences, in the key names
  3. You have an application running on an Amazon Elastic Compute Cloud instance, that uploads 5 GB video objects to Amazon Simple Storage Service (S3). Video uploads are taking longer than expected, resulting in poor application performance. Which method will help improve performance of your application?
    1. Enable enhanced networking
    2. Use Amazon S3 multipart upload
    3. Leveraging Amazon CloudFront, use the HTTP POST method to reduce latency.
    4. Use Amazon Elastic Block Store Provisioned IOPs and use an Amazon EBS-optimized instance
  4. Which of the following methods gives you protection against accidental loss of data stored in Amazon S3? (Choose 2)
    1. Set bucket policies to restrict deletes, and also enable versioning
    2. By default, versioning is enabled on a new bucket so you don’t have to worry about it (Not enabled by default)
    3. Build a secondary index of your keys to protect the data (improves performance only)
    4. Back up your bucket to a bucket owned by another AWS account for redundancy
  5. A startup company hired you to help them build a mobile application that will ultimately store billions of image and videos in Amazon S3. The company is lean on funding, and wants to minimize operational costs, however, they have an aggressive marketing plan, and expect to double their current installation base every six months. Due to the nature of their business, they are expecting sudden and large increases to traffic to and from S3, and need to ensure that it can handle the performance needs of their application. What other information must you gather from this customer in order to determine whether S3 is the right option?
    1. You must know how many customers that company has today, because this is critical in understanding what their customer base will be in two years. (No. of customers do not matter)
    2. You must find out total number of requests per second at peak usage.
    3. You must know the size of the individual objects being written to S3 in order to properly design the key namespace. (Size does not relate to the key namespace design but the count does)
    4. In order to build the key namespace correctly, you must understand the total amount of storage needs for each S3 bucket. (S3 provided unlimited storage the key namespace design would depend on the number)
  6. A document storage company is deploying their application to AWS and changing their business model to support both free tier and premium tier users. The premium tier users will be allowed to store up to 200GB of data and free tier customers will be allowed to store only 5GB. The customer expects that billions of files will be stored. All users need to be alerted when approaching 75 percent quota utilization and again at 90 percent quota use. To support the free tier and premium tier users, how should they architect their application?
    1. The company should utilize an amazon simple workflow service activity worker that updates the users data counter in amazon dynamo DB. The activity worker will use simple email service to send an email if the counter increases above the appropriate thresholds.
    2. The company should deploy an amazon relational data base service relational database with a store objects table that has a row for each stored object along with size of each object. The upload server will query the aggregate consumption of the user in questions (by first determining the files store by the user, and then querying the stored objects table for respective file sizes) and send an email via Amazon Simple Email Service if the thresholds are breached. (Good Approach to use RDS but with so many objects might not be a good option)
    3. The company should write both the content length and the username of the files owner as S3 metadata for the object. They should then create a file watcher to iterate over each object and aggregate the size for each user and send a notification via Amazon Simple Queue Service to an emailing service if the storage threshold is exceeded. (List operations on S3 not feasible)
    4. The company should create two separated amazon simple storage service buckets one for data storage for free tier users and another for data storage for premium tier users. An amazon simple workflow service activity worker will query all objects for a given user based on the bucket the data is stored in and aggregate storage. The activity worker will notify the user via Amazon Simple Notification Service when necessary (List operations on S3 not feasible as well as SNS does not address email requirement)
  7. Your company host a social media website for storing and sharing documents. the web application allow users to upload large files while resuming and pausing the upload as needed. Currently, files are uploaded to your php front end backed by Elastic Load Balancing and an autoscaling fleet of amazon elastic compute cloud (EC2) instances that scale upon average of bytes received (NetworkIn) After a file has been uploaded. it is copied to amazon simple storage service(S3). Amazon Ec2 instances use an AWS Identity and Access Management (AMI) role that allows Amazon s3 uploads. Over the last six months, your user base and scale have increased significantly, forcing you to increase the auto scaling groups Max parameter a few times. Your CFO is concerned about the rising costs and has asked you to adjust the architecture where needed to better optimize costs. Which architecture change could you introduce to reduce cost and still keep your web application secure and scalable?
    1. Replace the Autoscaling launch Configuration to include c3.8xlarge instances; those instances can potentially yield a network throughput of 10gbps. (no info of current size and might increase cost)
    2. Re-architect your ingest pattern, have the app authenticate against your identity provider as a broker fetching temporary AWS credentials from AWS Secure token service (GetFederation Token). Securely pass the credentials and s3 endpoint/prefix to your app. Implement client-side logic to directly upload the file to amazon s3 using the given credentials and S3 Prefix. (will not provide the ability to handle pause and restarts)
    3. Re-architect your ingest pattern, and move your web application instances into a VPC public subnet. Attach a public IP address for each EC2 instance (using the auto scaling launch configuration settings). Use Amazon Route 53 round robin records set and http health check to DNS load balance the app request this approach will significantly reduce the cost by bypassing elastic load balancing. (ELB is not the bottleneck)
    4. Re-architect your ingest pattern, have the app authenticate against your identity provider as a broker fetching temporary AWS credentials from AWS Secure token service (GetFederation Token). Securely pass the credentials and s3 endpoint/prefix to your app. Implement client-side logic that used the S3 multipart upload API to directly upload the file to Amazon s3 using the given credentials and s3 Prefix. (multipart allows one to start uploading directly to S3 before the actual size is known or complete data is downloaded)
  8. If an application is storing hourly log files from thousands of instances from a high traffic web site, which naming scheme would give optimal performance on S3?
    1. Sequential
    2. instanceID_log-HH-DD-MM-YYYY
    3. instanceID_log-YYYY-MM-DD-HH
    4. HH-DD-MM-YYYY-log_instanceID (HH will give some randomness to start with instead of instaneId where the first characters would be i-)
    5. YYYY-MM-DD-HH-log_instanceID