Hi @Denis_Bartashevich welcome to the community!
Are you seeing exactly the same thing, e.g. provisioned in AWS, write tickets numbers dropping, disk util %, iowait, etc.?
Generally if the disk appear to be maxed out, you might want to check if you’re using a burstable EBS type, which I think is the default setting in EC2. I have seen burstable EBS exhibit this exact behaviour: the disks seems to be underutilized but all signs point to overworked disks.
The typical solution is to provision a larger disk (since they usually have a larger burst credit), or move to a Provisioned IOPS disk with a setting that matches your needs.
See Amazon EBS volume types specifically the section titled I/O Credits and burst performance for more details about their behaviours.
Best regards
Kevin