Roland,
We have had good results with using Galera clusters with having multiple master DB servers which sounds like what you would need to do in your situation. I don't think Galera clusters are 100% supported by Moodle.org but I have not had any problems of collisions or corruptions.
I would recommend considering Andrew's suggestion further as it might be a solution for you as you can localize as much content as possible with caching (redis cluster?), localcachedir, moodle directory, opcache, etc while keeping the content that must be in a shared location for Moodle to use AWS. AWS does have solutions to distribute your data across the world and keep it in sync with their back-end methods.
I hope someone can correct me if I am wrong on the logic with MUC but think how your environment would work with AWS and properly configured caching and directories.
- 1st End user requests Content
- Moodle checks to see if it has a cache of the content
- If not, go to AWS to retrieve the content
- Moodle then makes a cache of the content
- Moodle delivers the content to the 1st end user
- 2nd user requests the same content
- Moodle checks to see if it has a cache of the content
- Moodle finds it has a cache of the content
- Moodle delivers it to the 2nd end user.
- 2nd user gets the content at near local speeds because it was already cached.
Question for our Moodle experts. Is there a way to tell Moodle to generate a cache everything in the environment?