How to store data in the web service database?

Question

PHP

Hello!
Asked a question of the correct architecture of a web service. Interested in how to organize data storage in an application similar to a CRM system with a scalability perspective.
Those. there are many users, each with their own set of clients, and so on.
From what I found:

• One table with clients of all users, in this table the Key with the value of the User
  
• Separate table with clients for each user, name User1_clients
  
• Separate database for each user
  
• On Habré I read about the virtualization option, when a virtual machine is created for each user with its own version of the web application and database
  

Question: Are there other options? which one is better in terms of scalability? which one is better in terms of development speed?
Are there examples of real web applications that tell how they store data?
Unfortunately, I did not find an English-language answer to a similar question. If there are links, I will be glad.

Answer 1

One table with clients of all users
the only reasonable option.
200-500-1000 clients? how to serve it?
Likewise. Infinite server resources? How to serve?

Answer 2

A separate table with clients for each user,
everything else is either unattended (I can’t imagine how to replicate 5000 databases),
or resource-intensive: in the first option, the database will respond to every sneeze