One of the common patterns tested on the AWS Certified Solutions Architect – Associate (SAA-C03) exam is identifying the right S3 upload strategy. These scenarios test whether you can design a solution that is resilient to network failures and operationally simple to implement.
To see how this plays out, let’s walk through a real-world scenario and the correct exam-aligned solution.
The Scenario
A field research team is capturing HD video recordings, each between 15 GB and 25 GB in size. These files must be uploaded into Amazon S3 for analysis and long-term storage.
The problem: the team relies on a satellite internet connection that frequently drops. Uploads often fail midway, forcing the entire process to restart, wasting both time and bandwidth.
The requirement:
The system must handle network failures gracefully.
Bandwidth should not be wasted when failures occur.
The process should require little ongoing management.
The Solution: Amazon S3 Multipart Upload
Amazon S3’s multipart upload feature addresses this challenge. Instead of sending the file as a single large object, it is divided into smaller parts. Each part can be uploaded independently and in parallel.
If a failure occurs, only the failed part is retried.
Parallel uploads shorten total transfer time.
The process is supported directly through the AWS SDKs and CLI with minimal operational effort.
When all parts are uploaded, Amazon S3 automatically assembles them into a single object.
S3 Upload Strategies
The core methods for uploading data directly into Amazon S3.
Upload Strategy | When to Use | Key Benefits |
|---|---|---|
Single PUT Upload | Small files (<100 MB) on stable networks | Simple, lowest overhead |
Multipart Upload | Large files (>100 MB; required for >5 GB) or unreliable networks | Parallel uploads, retries only failed parts, resilient and faster |
Pre-Signed URLs | Direct browser/mobile client uploads to S3 | Offloads backend, secure time-limited access, supports multipart |
AWS SDK Managed Upload | Application uploads where the SDK manages multipart and retries automatically | Simplifies development, resilient by default |
Operational Simplicity of S3 Upload Strategies
Strategy | Simplicity Level | Why It’s Simple / Complex | When It Stops Being Simple (or Why It’s More Complex) |
|---|---|---|---|
Single PUT Upload | Simple | Easiest — one API call ( | Only works well for small files (<100 MB). For larger files, retries mean restarting the entire upload |
AWS SDK Managed Upload | Simple | SDK handles multipart, retries, and error recovery automatically. Developers just call one method | You give up fine-grained control (e.g., part sizes, parallelism). For high-performance use cases, manual tuning may be better |
Pre-Signed URLs (with PUT) | Simple | Offloads responsibility to the client. Backend only generates a short-lived URL; no server-side data handling | Security and CORS setup must be managed correctly. Multipart with pre-signed URLs adds complexity |
Multipart Upload (manually managed) | Complex | Requires creating an upload ID, splitting files into parts, tracking part numbers, retrying failed parts, and calling | More moving parts; higher dev/ops effort compared to SDK-managed multipart |
Multipart with Pre-Signed URLs | Complex | Useful for client-side large uploads without routing through a backend | Backend must issue a signed URL for each part, client must track all parts and handle completion — adds significant complexity |
Data Transfer Services and Features Associated with S3 (and Exam Gotchas)
Broader mechanisms that move data into or within S3, plus common exam distractors.
Option | When to Use | Exam Traps / Notes |
|---|---|---|
S3 Transfer Acceleration | Data transfer into S3 from clients far from the bucket’s AWS Region | Improves throughput via AWS edge locations; does not fix unreliable networks |
AWS DataSync | Automated, large-scale on-prem → S3 transfers | Best for recurring migrations or millions of files |
AWS Snow Family (Snowball / Snowmobile) | Bulk offline transfer at TB/PB scale | Only correct if “petabyte-scale” or “limited network connectivity” |
S3 Lifecycle Policies | Transitioning objects between S3 storage classes | Does not ingest data into S3; classic exam distractor |
Amazon EC2 Staging Copy | Copying to EC2 first, then pushing to S3 | Adds cost and complexity; not exam-preferred |
Exam Highlights
On the SAA-C03 exam, expect questions like:
“A company must upload 20–30 GB files into Amazon S3 over an unreliable internet connection. Which solution minimizes retries and management effort?”
Correct: S3 Multipart Upload
Incorrect: Transfer Acceleration, Lifecycle Policies, EC2 staging
Patterns to recognize
File size over 5 GB → Multipart Upload
Unstable/flaky network → Multipart Upload
Global workforce uploads → Transfer Acceleration
Cost optimization between storage classes → Lifecycle Policies
Petabyte-scale offline → Snowball
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