An online judge is an online system to test programs in programming contests.The system can compile and execute code, and test them with pre-constructed data/test cases.But it is more than that.It should aso handle the performance isssue when handling multiple submissions and security of the system.
Performance related and security issues of naive system :
i) Becomes very slow when handling multiple submission
ii) halting of system due to malicious code
iii) Submission can consume the server’s bandwidth and disallow other submissions
iv) Access to other processes running and files in the system.