Fast global uploads to Amazon S3 — High-level Design + Practical Recipe

Short version: route clients to the nearest AWS edge, presign and push multipart uploads directly to S3 (or to a regional S3 endpoint behind a Multi-Region Access Point), and enable S3 Transfer Acceleration (or use Multi-Region Access Points + regional buckets) for global coverage. Add client-side multipart + parallelism, resumable retries, and instrumenting/monitoring. Below I give concrete architecture options (cheap → best global performance), the recommended flow, implementation tips, and trade-offs.

---

Key AWS building blocks (why you might use each)

• S3 Transfer Acceleration (TA) — uses CloudFront edge locations to accelerate long-distance PUT/POST to an S3 bucket. Easy to enable at the bucket level and often gives 50–500% speedups for long links. (AWS Documentation)
• S3 Multi-Region Access Points (MRAP) — provides a single global endpoint that routes requests to buckets in multiple AWS Regions (active/active or active/passive). Great for active-active multi-region architectures and lower latency by routing to the nearest replica. (AWS Documentation)
• CloudFront (edge) with PUT/POST support — CloudFront can forward PUT/POST to origins (custom origins or S3 with correct settings). Useful if you want control over authentication, WAF, or to hide S3. But CloudFront is not a direct replacement for Transfer Acceleration for S3 uploads. (Amazon Web Services, Inc.)
• AWS Global Accelerator — helps route traffic over the AWS global network and can be useful if you have TCP/UDP traffic or non-S3 origins; not S3-specific. Compare vs TA depending on use case. (Resilio)
• S3 Multipart Upload + presigned URLs — split large objects into parts, upload parts in parallel directly from client to S3 using presigned URLs (server issues presigned URLs). This minimizes server bandwidth/latency and supports resumable, parallel uploads. Essential for large files. (Amazon Web Services, Inc.)

---

Recommended architectures (pick by scale & needs)

Option A — Simple, low effort, global: S3 + Transfer Acceleration + presigned multipart

When you want the easiest global speed wins:

1. Enable S3 Transfer Acceleration on the target bucket.
2. On your backend (Lambda/EC2/API Gateway), create multipart upload and generate presigned URLs for each part (server signs PutObject/multipart parts).
3. Client uploads parts in parallel to the accelerated endpoint (<bucket>.s3-accelerate.amazonaws.com) using the presigned URLs.
4. Backend completes the multipart upload.

Why: minimal infra change, leverages AWS edge locations to speed long-distance uploads. Works well for mobile/web clients. (AWS Documentation)

Option B — High-scale, multi-region: Multi-Region Access Points + regional buckets + presigned multipart

When you need lowest possible latency worldwide, geo-redundancy, and fast failover:

1. Maintain replicated buckets (e.g., Cross-Region Replication or S3 Replicate) in 2+ Regions.
2. Create an S3 Multi-Region Access Point that covers those buckets.
3. Use the MRAP global endpoint for uploads; MRAP will route requests to the optimal region (and can fail over). Use presigned multipart URLs that target the MRAP endpoint or per-region endpoint as appropriate. Why: better locality (requests served to nearest region), built-in routing/failover for outages. (AWS Documentation)

Option C — Custom edge ingestion: CloudFront (configured for PUT/POST) → Regional API → presigned URLs or proxy

Use when you must inspect/authorize uploads at the edge or use WAF:

• Configure CloudFront to accept PUT/POST and point to a regional custom origin (your API).
• You can have CloudFront terminate TLS at the edge (lower RTT) and forward to your auth service, which returns presigned URLs or proxies upload streams to S3. Caveat: CloudFront puts an extra hop; for raw uploads to S3, TA or MRAP is simpler. (Amazon Web Services, Inc.)

---

Concrete client → server flow (best practice)

1. Client wants to upload file (small or large).
2. Client calls your backend auth endpoint (fast, lightweight) and sends metadata (size, filename, region preference if any).
3. Backend CreateMultipartUpload (or PutObject for small files) and generate presigned URLs for each part or for a single upload. (Use server SDK to create signed URLs with appropriate TTL and permissions.) (DEV Community)

4. Client uploads parts in parallel directly to the accelerated / MRAP endpoint using those presigned URLs (HTTP PUT). For each part capture ETag.

   • Use chunk sizes ≥5 MB (S3 multipart minimum), tune part size depending on average file size and network.
   • Use parallelism (e.g., 4–16 concurrent part uploads per client) and retry with exponential backoff for failed parts.
5. After all parts uploaded, client notifies backend to CompleteMultipartUpload with the parts list (ETags).
6. Backend optionally validates checksum, tags, etc., and finalizes.

---

Client-side tips for speed and reliability

• Parallel parts: upload multiple parts in parallel (but avoid saturating client bandwidth).
• Chunk sizing: small files → single put; large files → 8–64 MB parts often a good balance. Minimum 5 MB per part. (DEV Community)
• Resumable: keep state (uploaded part numbers, ETags) in local storage so uploads resume after network loss.
• Retries: implement idempotent retries per part and exponential backoff.
• Compression & dedupe: compress if beneficial; consider client-side hashing to detect duplicates and avoid reupload.
• Use SDK accelerated endpoint flag: many AWS SDKs support an accelerate endpoint option. (Amplify Documentation)

---

Security & cost considerations

• Presigned URLs limit exposure; set TTLs tight (minutes to hours depending on file size).
• CORS: ensure S3 CORS policy allows the required methods (PUT/POST/GET) for browser clients.
• Costs: Transfer Acceleration and MRAP add costs (TA charges per GB, MRAP routing charges). Test and measure — AWS will not charge TA if TA is not faster for a transfer. (Amazon Web Services, Inc.)
• WAF/inspection: if you need content inspection, route uploads through an API (higher cost/latency) or use Lambda to scan post-upload.

---

Observability and testing

• Enable S3 Server Access Logs or S3 Data Events + CloudTrail to trace uploads.
• Monitor S3 PutObject/Upload metrics in CloudWatch, and track client-side latency.
• Benchmark: run speed tests from target regions with and without TA/MRAP to choose the best option (AWS docs and blogs show TA gives variable improvements depending on location). (AWS Documentation)

---

Which option should you pick?

• If you want fast global wins with minimal change → Enable Transfer Acceleration + presigned multipart (Option A). Quick to implement and often effective. (AWS Documentation)
• If you want lowest latency everywhere + geo redundancy and can manage replication → MRAP + regional buckets (Option B). Better for massive global scale and compliance. (AWS Documentation)
• If you require edge authorization/WAF or custom logic at the edge → CloudFront + regional API (Option C). More complex and may not beat TA for raw upload latency. (Amazon Web Services, Inc.)

---

Quick checklist to implement now

1. Decide single-region vs multi-region (cost vs latency).
2. If single region, enable S3 Transfer Acceleration on the bucket. (AWS Documentation)
3. Implement server endpoint to start multipart upload and generate presigned URLs. (DEV Community)
4. Build client upload logic: parallel uploads, chunking, retries, resumability.
5. Add monitoring (CloudWatch metrics, S3 logs), and run speed tests from target geos to validate.

---