Questions
1 of 7
1How do I put files into S3?
2How do I take files out of S3?
3How can I make my files in S3 available to everyone?
4How can I automate moving files from my computer to S3?
5What are pre-signed URLs in S3, and how can they be used to grant temporary access to objects?
6Explain how to implement a serverless image resizing solution using S3 and Lambda.
7Describe a scenario where you would use S3 Select to query data directly from S3 objects without downloading the entire file.
AWS-s3AWS-s3
Basics
Buckets
Objects
Storage Classes
Data Access
01 / 07

How do I put files into S3?

You can upload files to Amazon S3 using the AWS Management Console, AWS CLI, or AWS SDKs. For files over 100 MB, multipart upload is recommended to improve performance and reliability.

Uploading files to S3 is a fundamental task, and AWS provides several tools to fit different use cases, from one-time manual uploads to automated, high-volume data pipelines. For objects larger than 100 MB, and especially mandatory for objects over 5 GB, you should use the Multipart Upload feature to ensure reliability [citation:3].

  1. 1

    Sign in to the AWS Management Console and open the Amazon S3 console.

  2. 2

    Navigate to the bucket where you want to upload your file.

  3. 3

    Click the 'Upload' button. You can then drag and drop files or folders, or use the 'Add files'/'Add folders' buttons to select them.

  4. 4

    Configure upload settings as needed (e.g., storage class, encryption, metadata).

  5. 5

    Click the 'Upload' button to start the upload.

The console is ideal for one-off uploads but not suitable for automating repetitive tasks [citation:2].

The AWS CLI is a command-line tool that allows you to manage S2 from your terminal. After installing and configuring it with aws configure, you can use the following commands [citation:2]:

Upload a single file
Upload a single file to a specific folder
Upload an entire directory
Upload with filters (only .jpg files)

For programmatic uploads within your applications, AWS provides SDKs for various languages like Python (boto3), JavaScript, Java, and others [citation:5][citation:6]. This method is essential for integrating S3 into your workflows.

Python (boto3) example

For large files (over 100MB), using a single PUT request can be slow and unreliable because a network interruption would force you to restart the entire upload. Multipart upload solves this by splitting the file into smaller chunks, uploading them independently, and then reassembling them on S3 [citation:1][citation:3]. This offers several benefits [citation:1][citation:3]:

  1. 1

    Resilience: If a part fails to upload, you only need to retry that specific part, not the entire file.

  2. 2

    Pause & Resume: You can pause an upload and resume it later.

  3. 3

    Parallel Uploads: You can upload multiple parts simultaneously, speeding up the process.

  4. 4

    Required for Files >5GB: While recommended for files over 100 MB, multipart upload is required for files larger than 5 GB [citation:3].

The AWS CLI and SDKs handle multipart uploads automatically for you when using commands like aws s3 cp or the upload_file method in boto3, simplifying the process [citation:3][citation:5].

  1. 1

    AWS Management Console: Best for simple, one-off uploads of a few files.

  2. 2

    AWS CLI: Perfect for scripting, automating uploads, and handling large batches of files.

  3. 3

    AWS SDKs: Essential for integrating S3 uploads directly into your applications, whether they are Python scripts, web applications, or mobile backends.

Difficulty: 5/10
Topics: upload methods, permissions, multipart upload

Scenario Questions

0-2 years experience
  1. 1

    We have a simple script that needs to copy a local log file to an S3 bucket. Walk me through the steps and the AWS CLI command you would use.

  2. 2

    If the bucket you’re uploading to has versioning enabled, what happens when you upload a file with the same key as an existing object?

  3. 3

    What IAM permissions does a user need to successfully upload a file to S3?

2-5 years experience
  1. 1

    Our service uploads user‑generated images to S3, but occasionally the upload fails with a 503 error. How would you investigate and mitigate this?

  2. 2

    Explain why you might choose multipart upload for large files and what parameters you would tune.

  3. 3

    If you need to ensure uploaded files are not publicly readable, how would you configure the bucket or request?

5-8 years experience
  1. 1

    Design a reliable file ingestion pipeline that writes files to S3 and guarantees exactly‑once delivery despite retries and partial failures.

  2. 2

    Discuss the trade‑offs between using S3 Transfer Acceleration versus a regional VPC endpoint for high‑throughput uploads.

  3. 3

    How would you handle uploading files larger than 5 GB while keeping latency low and ensuring resumable uploads?

8+ years experience
  1. 1

    Our organization is migrating terabytes of data from on‑premises storage to S3. What strategy would you propose to minimize cost, downtime, and data‑integrity risk?

  2. 2

    How would you design a cross‑team policy for managing S3 bucket lifecycle, encryption, and access controls at scale?

  3. 3

    If you need to serve billions of objects from S3 to a global audience, what architectural patterns would you employ to ensure low latency and high availability?

Follow-up Questions

  • ❓Can you walk me through how you’d implement retries for a failed upload?
  • ❓What metrics would you monitor to detect upload problems?
  • ❓How do you verify that the file arrived intact in S3?