https://fourtheorem.com/the-illustrated-guide-to-s3-pre-signed-urls/

Uploading and downloading files are very common features for most web and mobile applications.

But, implementing reliable and scalable upload and download workflows isn’t necessarily easy. You need to take care of storage, and permissions and maintain long-running connections between clients and your server.

If you are using a serverless architecture with API Gateway and Lambda,  implementing upload and download functionalities gets even more complicated because you are constrained by strict payload size limits (Lambda request/response payloads are both limited to 6 MB) and time limits (API Gateway will timeout after 29 seconds).

So, how can we implement upload and download functionality in an easy yet reliable way on AWS?

The simple answer is to use S3 and leverage S3 pre-signed URLs. In this article, we will discuss in great detail what pre-signed URLs are, how to use them, and some best practices to keep in mind.