Top AWS S3 Interview Questions and Answers

Introduction

Amazon S3, or Simple Storage Service, is a crucial part of AWS, allowing users to store and retrieve data quickly. It's like a giant online storage locker where you can keep all sorts of files, from documents to images. What's great is that it's super reliable, scalable, and affordable. For beginners in AWS interviews, understanding S3 basics is critical. You can impress interviewers by explaining how S3 works, its features like versioning and encryption, and how it's used for static website hosting.

Q1: What Is AWS S3?

A: AWS S3 is like a giant online storage space where we can keep a lot of data and easily access it. It's suitable for big projects because it can handle vast amounts of data, up to 5TB per file. It's not only suitable for storing data, but it's also fast and costs little compared to other similar services.

Q2: What Is An S3 Bucket?

A: An S3 bucket is a folder where you store your files. You can have many buckets, and each bucket can hold many files. A file can be anything like a document or an image. You can easily manage your files in buckets by adding, deleting, or changing them.

Q3: What's The Connection Between Instance And AMI?

A: An AMI is like a blueprint for setting up a virtual server, called an instance, on AWS. You can create different instances from the same AMI, like setting up servers for different purposes.

Q4: What Are Buckets In Amazon S3?

A: A bucket is a container (web folder) for objects (files) stored in Amazon S3. Every Amazon S3 object is contained in a bucket. Buckets form the top-level namespace for Amazon S3, and bucket names are global. This means your bucket names must be unique across all AWS accounts, much like Domain Name System (DNS) domain names, not just within your account. Bucket names can contain up to 63 lowercase letters, numbers, hyphens, and periods. You can create and use multiple buckets, with up to 100 per account by default.

Q5: What Is Static Website Hosting In S3?

A: Hosting a static website in S3 means storing simple HTML, CSS, or JavaScript files in an S3 bucket and using that bucket as a web server. AWS has other services for hosting dynamic websites.

To set up a static website in an S3 bucket, upload your HTML file to the bucket. Then, in the bucket settings, look for the 'Static Website Hosting' option. Please enable it and specify the name of the index document you uploaded. For simplicity, ensure the index document is in the root of the S3 bucket.

Q6: What Are Some Amazon S3 Operations?

A: The Amazon S3 API is intentionally simple, with only a handful of joint operations. They include:

• Create/delete a bucket

• Write an object

• Read an object

• Delete an object

• List keys in a bucket

Q7: What Kind Of Information Does Logs Include?

A: Once enabled, logs are delivered on a best-effort basis with a slight delay. Logs include information such as:

• Requestor account and IP address

• Bucket name

• Request time

• Action (GET, PUT, LIST, and so forth)

• Response status or error code

Q8: Explain The Steps Of Creating S3 Buckets.

A: Log in to the AWS Management Console and go to S3. Click on the 'create bucket' option. This will start a wizard to create the bucket. Please enter your desired bucket name (remember, it must be unique). Choose the region where you want to create the bucket. You can also copy settings from an existing bucket if you want. Configure public access settings, enable bucket versioning, and set up encryption if needed. In advanced settings, you can enable Object Lock. Finally, click 'Create Bucket' to finish

Q9: Describe How S3 And EBS Vary From One Another.

A: Both Amazon S3 and Amazon EBS are storage services provided by AWS, but they have different purposes. S3 can store and retrieve any amount of data at any time, making it great for static files, backups, and web content.

On the other hand, EBS provides block-level storage volumes that you can use with EC2 instances to store data persistently. It's best for applications that need a database, file system, or direct access to raw storage blocks.

Q10: What Are AWS Regions?

A: Even though the namespace for Amazon S3 buckets is global, each Amazon S3 bucket is created in a specific region you choose. This lets you control where your data is stored. You can create and use buckets close to a particular set of end users or customers to minimize latency, located in a particular region to satisfy data locality and sovereignty concerns, or located far away from your primary facilities to satisfy disaster recovery and compliance needs. You control the location of your data; data in an Amazon S3 bucket is stored in that region unless you explicitly copy it to another bucket in a different region

Q11: What Are The Different Types Of Virtualization In AWS?

A: There are three types:

HVM (Hardware Virtual Machine): This fully virtualizes the hardware, so each virtual machine acts independently. It's like they have their virtual hardware. When you start an AWS virtual machine, its boot process runs.

PV (Paravirtualization): This is a lighter virtualization form than HVM. The guest operating system needs some tweaking before it can work. These tweaks help export a simpler version of hardware to virtual machines.

PV on HVM: This combination of HVM and PV benefits is like a middle ground where operating systems can access storage and network resources through the host system.

Q12: How Can You Add Another Layer Of Protection On Top Of Bucket Versioning?

A: MFA Delete adds another layer of data protection to bucket versioning. It requires additional authentication to permanently delete an object version or change the versioning state of a bucket. In addition to your normal security credentials, MFA Delete requires an authentication code (a temporary, one-time password) generated by a hardware or virtual Multi-Factor Authentication (MFA) device. Note that MFA Delete can only be enabled by the root account.

Q13: How Can An Object Owner Share An Amazon S3 Object With Others?

A: All Amazon S3 objects by default are private, meaning only the owner has access. However, the object owner can optionally share objects with others by creating a pre-signed URL, using their security credentials to grant time-limited permission to download the objects. When you create a pre-signed URL for your object, you must provide your security credentials and specify a bucket name, an object key, the HTTP method (GET to download the object), and an expiration date and time. The pre-signed URLs are valid only for the specified duration. This is particularly useful in protecting against "content scraping" of web content, such as media files stored in Amazon S3.

Q14: How Can You Replicate New Objects To Target Buckets In Another Region?

A: Cross-region replication is a feature of Amazon S3 that allows you to asynchronously replicate all new objects in the source bucket in one AWS region to a target bucket in another region. Any metadata and ACLs associated with the object are also part of the replication. 

After you set up cross-region replication on your source bucket, any changes to the data, metadata, or ACLs on an object trigger a new replication to the destination bucket. To enable cross-region replication, versioning must be turned on for both source and destination buckets, and you must use an IAM policy to permit Amazon S3 to replicate objects on your behalf.

Cross-region replication is commonly used to reduce the latency required to access objects in Amazon S3 by placing objects closer to a set of users or to meet requirements to store backup data at a certain distance from the source data

Q15: Explain Data Durability And Availability.

A: Data durability and availability are related but slightly different concepts. Durability addresses the question, "Will my data still be there in the future?" Availability addresses the question, "Can I access my data right now?" Amazon S3 is designed to provide very high durability and availability for your data.

Amazon S3 standard storage is designed for 99.999999999% durability and 99.99% availability of objects over a given year. For example, if you store 10,000 objects with Amazon S3, you can expect to incur a loss of a single object once every 10,000,000 years. Amazon S3 achieves high durability by automatically storing data redundantly on multiple devices in regional facilities. It is designed to sustain the concurrent data loss in two facilities without loss of user data. Amazon S3 provides a highly durable infrastructure for mission-critical and primary data storage.

Suppose you need to store non-critical or easily reproducible derived data (such as image thumbnails) that doesn't require this high level of durability. In that case, you can use Reduced Redundancy Storage (RRS) at a lower cost. RRS offers 99.99% durability at a lower cost than traditional Amazon S3 storage.

Q16: Explain Data Consistency

A: Amazon S3 will eventually be a consistent system. Because your data is automatically replicated across multiple servers and locations within a region, changes in your data may take some time to propagate to all locations. As a result, in some situations, the information you read immediately after an update may return stale data.

This is not a concern for PUTs to new objects—in this case, Amazon S3 provides read-after-write consistency. However, for PUTs to existing objects (object overwrite to an existing key) and for object DELETEs, Amazon S3 provides eventual consistency.

Eventual consistency means that if you PUT new data to an existing key, a subsequent GET might return the old data. Similarly, if you DELETE an object, a subsequent GET for that object might still read the deleted object. In all cases, updates to a single key are atomic—for eventually consistent reads, you will get the new or old data, but never an inconsistent mix of data.

Q17: How Can You Give Access Control To Others On Amazon S3?

A: Amazon S3 is secure by default; you have access only when you create a bucket or object in Amazon S3. To allow you to give controlled access to others, Amazon S3 provides both coarse-grained access controls (Amazon S3 Access Control Lists [ACLs]) and fine-grained access controls (Amazon S3 bucket policies, AWS Identity and Access Management [IAM] policies, and query-string authentication).

Amazon S3 ACLs allow you to grant specific coarse-grained permissions: READ, WRITE, or FULL-CONTROL at the object or bucket level. ACLs are a legacy access control mechanism created before IAM existed. They are best used today for a limited set of use cases, such as enabling bucket logging or making a bucket that hosts a static website world-readable.

Amazon S3 bucket policies are the recommended access control mechanism for Amazon S3 and provide much finer-grained control. Amazon S3 bucket policies are very similar to IAM policies "AWS Identity and Access Management (IAM)," but are subtly different in that:

• They are associated with the bucket resource instead of an IAM principal.

• They include an explicit reference to the IAM principal in the policy. This principle can be associated with a different AWS account, so Amazon S3 bucket policies allow you to assign cross-account access to Amazon S3 resources.

Using an Amazon S3 bucket policy, you can specify who can access the bucket, from where (by Classless Inter-Domain Routing [CIDR] block or IP address), and during what time of day.

Finally, IAM policies may be associated directly with IAM principals that grant access to an Amazon S3 bucket, just as it can grant access to any AWS service and resource. You can only assign IAM policies to the principals you control in AWS accounts.

Q18: What Is The Use Of Prefixes And Delimiters?

A: While Amazon S3 uses a flat structure in a bucket, it supports using prefix and delimiter parameters when listing key names. This feature lets you hierarchically organize, browse, and retrieve the objects within a bucket. Typically, you would use a slash (/) or backslash (\) as a delimiter and then use critical names with embedded delimiters to emulate a file and folder hierarchy within a bucket's flat object key namespace.

For example, you might want to store a series of server logs by server name (such as server42) but organized by year and month, like so:

• logs/2016/January/server42.log

• logs/2016/February/server42.log

• logs/2016/March/server42.log

The REST API, wrapper SDKs, AWS CLI, and the Amazon Management Console all support delimiters and prefixes. This feature lets you logically organize new data and easily maintain the hierarchical folder-and-file structure of existing data uploaded or backed up from traditional file systems. Used together with IAM or Amazon S3 bucket policies, prefixes and delimiters also allow you to create the equivalent of departmental "subdirectories" or user "home directories" within a single bucket, restricting or sharing access to these "subdirectories" (defined by prefixes) as needed.

Q19: What Are The Types Of Storage Casses Amazon S3 Offers?

A: Amazon S3 offers a range of storage classes suitable for various use cases.

Amazon S3 Standard offers high durability, high availability, low latency, and high-performance object storage for general purpose use. Because it delivers low first-byte latency and high throughput, Standard is well-suited for short-term or long-term storage of frequently accessed data. Amazon S3 Standard is the place to start for most general-purpose use cases.

Amazon S3 Standard – Infrequent Access (Standard-IA)– offers the same durability, low latency, and high throughput as Amazon S3 Standard but is designed for long-lived, less frequently accessed data. Standard-IA has a lower per GB-month storage cost than Standard. Still, the price model also includes a minimum object size (128KB), minimum duration (30 days), and per-GB retrieval costs, so it is best suited for infrequently accessed data stored for over 30 days.

Amazon S3 Reduced Redundancy Storage (RRS)– offers slightly lower durability (4 nines) than Standard or Standard-IA at a reduced cost. It is most appropriate for derived data that can be easily reproduced, such as image thumbnails.

Amazon Glacier– storage class offers secure, durable, and extremely low-cost cloud storage for data that does not require real-time access, such as archives and long-term backups. To keep costs low, Amazon Glacier is optimized for infrequently accessed data where a retrieval time of several hours is suitable. 

To retrieve an Amazon Glacier object, you issue a restore command using one of the Amazon S3 APIs; three to five hours later, the Amazon Glacier object is copied to Amazon S3 RRS. Note that the restore creates a copy in Amazon S3 RRS; the original data object remains in Amazon Glacier until explicitly deleted.

Q20: What Is Object Lifecycle Management In Amazon S3?

A: Amazon S3 Object Lifecycle Management is equivalent to automated storage tiering in traditional IT infrastructures. In many cases, data has a natural lifecycle, starting as "hot" (frequently accessed) data, moving to "warm" (less frequently accessed) data as it ages, and ending its life as "cold" (long-term backup or archive) data before eventual deletion.

For example, many business documents are frequently accessed when created, then become much less frequently accessed over time. In many cases, however, compliance rules require business documents to be archived and kept accessible for years. Similarly, studies show that file, operating system, and database backups are most frequently accessed in the first few days after they are created, usually to restore after an inadvertent error. After a week or two, these backups remain a critical asset, but they are much less likely to be accessed for a restore. Compliance rules often require several backups to be kept for several years

Conclusion

JanBask Training's AWS courses that cover S3 comprehensively. Their courses provide hands-on experience, teaching how to create S3 buckets, upload files, and configure permissions. Understanding S3 through JanBask's courses can give you an edge in interviews, showcasing practical skills. Moreover, JanBask's interactive learning approach helps beginners grasp complex concepts quickly. With JanBask Training's AWS courses, you not only learn about S3 but also gain confidence to ace AWS interviews and excel in cloud computing careers.