capturing and uploading a whole new PNG for each screencap is not what I would call 'efficient', and to meet the use case of Rewind.ai in the first place it should have some OCR mechanism to pull up the relevant screencaps.
The thing that enabled rewind.ai and MS Recall is storing the series of screenshots more like a HEIF, allowing for massive compression ratio and on-device storage + OCR provided by the OS (Live Text since Monterey 2021 [0], Microsoft introduced it last year for Snapdragon based AI-PCs [1])
I guess this is a good starting point if the goal is to fill S3 buckets with screencaps of multiple users, but then we're just back to corporate spyware, not tools for helping individuals use their machine more effectively.
That said, if I was using my own minio backend, it would be neat to archive my screen captures but I would change it so it captures after, say, every keystroke, and every time my mouse stops moving, and after every click. That way I have high density capture of taking actions, and low density otherwise. In any case collecting the data is not the issue, making an interface where that data becomes useful to help me remember something is.
[0] https://support.apple.com/guide/preview/interact-with-text-i...
[1] https://learn.microsoft.com/en-us/windows/ai/apis/text-recog...