Different file versions in different geographical locations

On 2 separate occasions now, I’ve uploaded a file to a droplet from my location in Canada, but users viewing the site in the UK are seeing the old version of the file.

The first time this happened I uploaded a stylesheet. The stylesheet updated for me and other users in North America, but users in the UK were still being served the original stylesheet, even after clearing their browser caches. In this case, I restarted the droplet which fixed the issue.

The second time this happened was 2 days ago, I uploaded an updated logo in svg format. I deleted the original file and uploaded the new one which had the same filename and path. I could see the updated logo along with other users in North America, but users in the UK were still seeing the original logo. In this case, I don’t know if they cleared their caches or if a droplet restart fixed the issue.

I was hoping someone had an explanation for why this happens, and how to avoid it in the future?