AWS Certification Exam Prep: S3 Facts, Summaries, Questions and Answers
Definition 1: Amazon S3 or Amazon Simple Storage Service is a “simple storage service” offered by Amazon Web Services that provides object storage through a web service interface. Amazon S3 uses the same scalable storage infrastructure that Amazon.com uses to run its global e-commerce network.
Definition 2: Amazon Simple Storage Service (Amazon S3) is an object storage service that offers industry-leading scalability, data availability, security, and performance.
AWS S3 Explained graphically:
AWS S3 Facts and summaries
- S3 is a universal namespace, meaning each S3 bucket you create must have a unique name that is not being used by anyone else in the world.
- S3 is object based: i.e allows you to upload files.
- Files can be from 0 Bytes to 5 TB
- What is the maximum length, in bytes, of a DynamoDB range primary key attribute value?
The maximum length of a DynamoDB range primary key attribute value is 2048 bytes (NOT 256 bytes).
- S3 has unlimited storage.
- Files are stored in Buckets.
- Read after write consistency for PUTS of new Objects
- Eventual Consistency for overwrite PUTS and DELETES (can take some time to propagate)
- S3 Storage Classes/Tiers:
- S3 Standard (durable, immediately available, frequently accesses)
- Amazon S3 Intelligent-Tiering (S3 Intelligent-Tiering): It works by storing objects in two access tiers: one tier that is optimized for frequent access and another lower-cost tier that is optimized for infrequent access.
- S3 Standard-Infrequent Access – S3 Standard-IA (durable, immediately available, infrequently accessed)
- S3 – One Zone-Infrequent Access – S3 One Zone IA: Same ad IA. However, data is stored in a single Availability Zone only
- S3 – Reduced Redundancy Storage (data that is easily reproducible, such as thumbnails, etc.)
- Glacier – Archived data, where you can wait 3-5 hours before accessing
You can have a bucket that has different objects stored in S3 Standard, S3 Intelligent-Tiering, S3 Standard-IA, and S3 One Zone-IA.
- The default URL for S3 hosted websites lists the bucket name first followed by s3-website-region.amazonaws.com . Example: enoumen.com.s3-website-us-east-1.amazonaws.com
- Core fundamentals of an S3 object
- Key (name)
- Value (data)
- Version (ID)
- Sub-resources (used to manage bucket-specific configuration)
- Bucket Policies, ACLs,
- Transfer Acceleration
- Object-based storage only for files
- Not suitable to install OS on.
- Successful uploads will generate a HTTP 200 status code.
- S3 Security – Summary
- By default, all newly created buckets are PRIVATE.
- You can set up access control to your buckets using:
- Bucket Policies – Applied at the bucket level
- Access Control Lists – Applied at an object level.
- S3 buckets can be configured to create access logs, which log all requests made to the S3 bucket. These logs can be written to another bucket.
- S3 Encryption
- Encryption In-Transit (SSL/TLS)
- Encryption At Rest:
- Server side Encryption (SSE-S3, SSE-KMS, SSE-C)
- Client Side Encryption
- Remember that we can use a Bucket policy to prevent unencrypted files from being uploaded by creating a policy which only allows requests which include the x-amz-server-side-encryption parameter in the request header.
- S3 CORS (Cross Origin Resource Sharing):
CORS defines a way for client web applications that are loaded in one domain to interact with resources in a different domain.
- Always use the S3 website URL, not the regular bucket URL. E.g.: https://s3-eu-west-2.amazonaws.com/acloudguru
- S3 CloudFront:
- Edge locations are not just READ only – you can WRITE to them too (i.e put an object on to them.)
- Objects are cached for the life of the TTL (Time to Live)
- You can clear cached objects, but you will be charged. (Invalidation)
- S3 Performance optimization – 2 main approaches to Performance Optimization for S3:
- GET-Intensive Workloads – Use Cloudfront
- Mixed Workload – Avoid sequencial key names for your S3 objects. Instead, add a random prefix like a hex hash to the key name to prevent multiple objects from being stored on the same partition.
- The best way to handle large objects uploads to the S3 service is to use the Multipart upload API. The Multipart upload API enables you to upload large objects in parts.
- You can enable versioning on a bucket, even if that bucket already has objects in it. The already existing objects, though, will show their versions as null. All new objects will have version IDs.
- Bucket names cannot start with a . or – characters. S3 bucket names can contain both the . and – characters. There can only be one . or one – between labels. E.G mybucket-com mybucket.com are valid names but mybucket–com and mybucket..com are not valid bucket names.
- What is the maximum number of S3 buckets allowed per AWS account (by default)? 100
- You successfully upload an item to the us-east-1 region. You then immediately make another API call and attempt to read the object. What will happen?
All AWS regions now have read-after-write consistency for PUT operations of new objects. Read-after-write consistency allows you to retrieve objects immediately after creation in Amazon S3. Other actions still follow the eventual consistency model (where you will sometimes get stale results if you have recently made changes)
- S3 bucket policies require a Principal be defined. Review the access policy elements here
- What checksums does Amazon S3 employ to detect data corruption?
Amazon S3 uses a combination of Content-MD5 checksums and cyclic redundancy checks (CRCs) to detect data corruption. Amazon S3 performs these checksums on data at rest and repairs any corruption using redundant data. In addition, the service calculates checksums on all network traffic to detect corruption of data packets when storing or retrieving data.
AWS S3 Top 10 Questions and Answers Dump
Q0: You’ve written an application that uploads objects onto an S3 bucket. The size of the object varies between 200 – 500 MB. You’ve seen that the application sometimes takes a longer than expected time to upload the object. You want to improve the performance of the application. Which of the following would you consider?
- A. Create multiple threads and upload the objects in the multiple threads
- B. Write the items in batches for better performance
- C. Use the Multipart upload API
- D. Enable versioning on the Bucket
Q2: You are using AWS SAM templates to deploy a serverless application. Which of the following resource will embed application from Amazon S3 buckets?
- A. AWS::Serverless::Api
- B. AWS::Serverless::Application
- C. AWS::Serverless::Layerversion
- D. AWS::Serverless::Function
- A. Enable versioning for the underlying S3 bucket.
- B. Enable Replication so that the objects get replicated to the other bucket
- C. Enable CORS for the bucket
- D. Change the Bucket policy for the bucket to allow access from the other bucket
Q4: Your mobile application includes a photo-sharing service that is expecting tens of thousands of users at launch. You will leverage Amazon Simple Storage Service (S3) for storage of the user Images, and you must decide how to authenticate and authorize your users for access to these images. You also need to manage the storage of these images. Which two of the following approaches should you use? Choose two answers from the options below
- A. Create an Amazon S3 bucket per user, and use your application to generate the S3 URL for the appropriate content.
- B. Use AWS Identity and Access Management (IAM) user accounts as your application-level user database, and offload the burden of authentication from your application code.
- C. Authenticate your users at the application level, and use AWS Security Token Service (STS)to grant token-based authorization to S3 objects.
- D. Authenticate your users at the application level, and send an SMS token message to the user. Create an Amazon S3 bucket with the same name as the SMS message token, and move the user’s objects to that bucket.
Q5: Both ACLs and Bucket Policies can be used to grant access to S3 buckets. Which of the following statements is true about ACLs and Bucket policies?
- A. Bucket Policies are Written in JSON and ACLs are written in XML
- B. ACLs can be attached to S3 objects or S3 Buckets
- C. Bucket Policies and ACLs are written in JSON
- D. Bucket policies are only attached to s3 buckets, ACLs are only attached to s3 objects
Q6: What are good options to improve S3 performance when you have significantly high numbers of GET requests?
- A. Introduce random prefixes to S3 objects
- B. Introduce random suffixes to S3 objects
- C. Setup CloudFront for S3 objects
- D. Migrate commonly used objects to Amazon Glacier
Q7: 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?
- A. Sequential
- B. HH-DD-MM-YYYY-log_instanceID
- C. YYYY-MM-DD-HH-log_instanceID
- D. instanceID_log-HH-DD-MM-YYYY
- E. instanceID_log-YYYY-MM-DD-HH
Q8: You are working with the S3 API and receive an error message: 409 Conflict. What is the possible cause of this error
- A. You’re attempting to remove a bucket without emptying the contents of the bucket first.
- B. You’re attempting to upload an object to the bucket that is greater than 5TB in size.
- C. Your request does not contain the proper metadata.
- D. Amazon S3 is having internal issues.
Q9: You created three S3 buckets – “mywebsite.com”, “downloads.mywebsite.com”, and “www.mywebsite.com”. You uploaded your files and enabled static website hosting. You specified both of the default documents under the “enable static website hosting” header. You also set the “Make Public” permission for the objects in each of the three buckets. You create the Route 53 Aliases for the three buckets. You are going to have your end users test your websites by browsing to http://mydomain.com/error.html, http://downloads.mydomain.com/index.html, and http://www.mydomain.com. What problems will your testers encounter?
- A. http://mydomain.com/error.html will not work because you did not set a value for the error.html file
- B. There will be no problems, all three sites should work.
- C. http://www.mywebsite.com will not work because the URL does not include a file name at the end of it.
- D. http://downloads.mywebsite.com/index.html will not work because the “downloads” prefix is not a supported prefix for S3 websites using Route 53 aliases
Q10: Which of the following is NOT a common S3 API call?
- A. UploadPart
- B. ReadObject
- C. PutObject
- D. DownloadBucket
Other AWS Facts and Summaries
- AWS S3 facts and summaries
- AWS DynamoDB facts and summaries
- AWS EC2 facts and summaries
- AWS Lambda facts and summaries
- AWS SQS facts and summaries
- AWS RDS facts and summaries
- AWS ECS facts and summaries
- AWS CloudWatch facts and summaries
- AWS SES facts and summaries
- AWS EBS facts and summaries
- AWS Serverless facts and summaries
- AWS ELB facts and summaries
- AWS Autoscaling facts and summaries
- AWS VPC facts and summaries
- AWS KMS facts and summaries
- AWS Elastic Beanstalk facts and summaries
- AWS CodeBuild facts and summaries
- AWS CodeDeploy facts and summaries
- AWS CodePipeline facts and summaries