Hello @Vlad Mihalcea,
I see this issue is assigned to you. Are you currently working on a fix for this? If so I have some code that you might find useful to provide a better sequence emulation than the current TABLE generator is using.

It uses separate rows in the sequence table for each entity so different entities are not competing for a lock. It also uses a buffer and a variable fetch size configurable for each entity so that in high throughput systems a block of IDs can be requested with a single DB query and then dolled out as needed.

I have been using this code for over 10 years in various high throughput applications with great success. With minor modification if could be generalized for other Hibernate MySQL users.

Let me know if you are interested and I can provide you with the code.