@Juri Writes per second hugely depends on number of alphas. I was able to load test ~9000writes/sec with 3 alpha-zero node each had 128G RAM and 64Core CPUs. Also number of reads were something near that number but it was related to query and number of touched nodes.
If your writes exceeds the timeout limit of alphas then they are going to get aborted, otherwise it might take little bit longer.
In your case I think you can use Ludicrous mode for better performance.