It does not matter if your modern server has an SSD or not, beanstalkd is MEMORY/CPU bound but not DISK bound if you don't need any persistence. So you had 25k/sec how big was your avg. message? I saw a somewhat hard barrier at about 20MB/s traffic for about 10K messages with avg. size of 2KB. With redis I was able to increase the performance by a factor of 10 on the same hardware.