SharePoint 429 Error - Throttling

We have encountered again error 429 and also error 503 last week. Although we haven't seen any more in the past 4 days, we are curious again on what might have triggered this issue. We have told our users to not use SharePoint for the time being, so that might have helped in stopping these errors, but we cannot say for sure.

From our end, the only new change we did is that we started evaluating a 3rd party software (Metalogix) to take a backup of our Office 365 solution. Our tests were mainly backing up of 2 small mailboxes (multiple times due to different tests) to our Azure blob storage.

Would it be possible that our solution (previously mentioned) together with Metalogix caused this issue again?

All we would like to know is:

1. How are we being throttled?

2. How could we know what is causing the throttling?

3. What are our limits?

Currently we are in a situation where the company is constantly growing and of course we are constantly increasing the adoption of Office 365 to all our users, especially in SharePoint and Teams. Our fear is that if we increase more usage and applications on our Office 365 solution, the more we are going to encounter these throttling issues. So without having any information on the 3 points mentioned above, we cannot plan any future applications on SharePoint.

Does anyone encountered the same issue lately?