Take away the word micro from micro services. Its just a buzzword. Now you have just services. You can have just one service that handles email, chat, payroll, website - or you can break them up into independent services. Ask yourself: Does it make sense to have two different services to handle x and y. Just don't break something up because of some buzzword mantra. Maybe the public website is the bottleneck in your monolith, then it might be a good idea to put it on its own server and scaling strategy so that it doesn't bog down the other parts of the system.