Just 10,000 visitors per day on a 64 core machine with 256GB of RAM? If were per minute (or even hour) it would make sense, otherwise, it seems poorly designed.
If it is just static content then you should be able to saturate your uplink from one single machine.
The 10K number applied to the whole setup, and that's now comfortably served from one box (as it should be). It could probably handle 10 times that number now without too much in terms of additional tuning (if any), above that it might require more work.
I have seen caches having more inserts v/s reads.
I have seen them replacing MySQL by NoSQL as it does not scale for them.
This is common for early stage funded startups founded by non tech founders.
"Let's make our change password system handle 100k requests per minute but the front page starts to get wonky at 1000 req/min"
Only time this table is touched to check user entered correct password or not.
Are they just logging in twice a day to punch in/out, like a online timeclock? Certainly too many resources for that amount of traffic.
But are each of the 10,000 users logged in all day, each working with large files or data sets, and doing intensive tasks?
How much space does the client need for this trading app? DBA figures 1k transactions per day at 1kb/record for 1 MB storage, round that up to 1 GB per year, so tell them 10 GB should do for 10 years.
CTO hears 10 GB from the DBA, adds his own safety margin factor of 10x, tells the client 100 GB.
Client hears 100 GB, adds his own safety margin factor of 10x, tells their operations 1 TB.
So now we have a client building a giant SCSI terabyte array (this was when 72 GB SCSI disks were the high end server standard) to hold a database that's a year away from reaching even one gigabyte.