MySQL Connection Error on heavy load with wordpress site

Question

I've used WordPress site, If we give multiple requests using JMeter or on search engine boot time MySQL server getting down

I have changed the below configuration on my server

• key_buffer = 25M
• max_allowed_packet = 1M
• thread_stack = 128K
• table_cache = 25
• innodb_buffer_pool_size= "64M" to "512M"
• max_connections = 200;

How to fix the issue?

This issue happens only on high traffic like 200 to 500 request at a time