bug caught in production why it wasn't catch in test environment

Answer:
	Initially we need to check if the issue reported in
    Prod environment is a valid defect. If so:
	1. The test environment is different from Production environment.
    Exp: Access & Permissions in Prod environment,
    Memory limitations, ELB timeout, Single & Multi-tenant
    configs etc is different.
	2. Tester doesn't test that scenario or he may test 
    it in a different way.
	3. There might be an issue regarding Timezone server time.
	4. One common reason for this behaviour is
    production data schema differs when we add new features 
    and if not updated or correctly replicated on all servers
    it might create production issues.
	5. Exhaustive testing is also not possible. ==> 
    We cannot test everything.
	6. Code is not migrated to Production environment properly,
    there might be some issues in migrating the code for that
    particular functionality where the issues caught.
	7. There might be requirement gap.
	8. Verify if Prod and QA had similar internet connectivity
    setup (like VPN, LAN, Wifi)