Php script - need to improve caching mechanism and optimizing mysql queries.Getting internal server 500 error due to heavy load by ertem84

Hello, i have an php video script(custom written) on my web site,including legal adult content.It has heavy loading issue. When online users excess number of 1k, apache server giving internal server 500... (Budget: $10-$30 USD, Jobs: Database Administration, MySQL, PHP, Software Architecture, Website Management)