Hey Odooers!

​I'm very stuck with my server. I've hosted my odoo server on amazon aws. Odoo server RAM is 16 GB , CPU is 8 cores . There will be only maxmum 100 concurrent users . Odoo works fine  . But there is an automated workflow in sale module . When customer bought something , sale record is created then invoice  in invoice module and journal entires in inventory module are automatically created. When we confirm our sales , it sometimes took at least 50 seconds and loading screen appears very long.  It occasionally went into forever loading screen. Note that it didn't always happen . I though I need to configure my server and postgresql well. Thus , please tell me the best configuration suited with our server