WordPress using MySQL keeps on crashing

Hi,

We are currently running WordPress 4.1.1 and using MySQL version 5.5.

We have about 10000+ blog users and I was wondering why we are always experiencing downtime. The errors are mostly saying “error establishing database connection”. I checked the MySQL performance and its CPU Memory is hitting 100%. Please take note that I had wordpress web contents installed in a different server from the DB server.

Here’s the details from my.ini in MySQL files:
max_connections=800
query_cache_size=350M
table_open_cache=1520
tmp_table_size=125M
thread_cache_size=38
myisam_max_sort_file_size=100G
myisam_sort_buffer_size=125M
key_buffer_size=548M
read_buffer_size=64K
read_rnd_buffer_size=256K
sort_buffer_size=256K

Appreciate your suggestions in advance. Thanks!