Multi Tenants Overview:
Multi-tenancy is an architecture in which a single instance of a software application serves multiple customers. Each customer is called a tenant. Tenants may be given the ability to customize some parts of the application, such as color of the user interface (UI) or business rules, but they cannot customize the application’s code. In the case of EBay each customer has an option to display his or her page that is called a store. What is super fascinating is how the Data base is configured.

Multi Tenants Database Architecture:
It is used to address the problem of SAAS which can serve multiple clients. Multi-Tenants database architecture is very useful when one instance of database is serving to multiple clients. Only one set of hardware resources is needed to fulfill the requirements of all users.

There are different approaches to the advantage out of the multi-tenants database. These are

• Dedicated database: Separate databases per tenant.
• Dedicated table and different schema:  Shared database and separate schema.
• Share table/schema: Same database and same table.

1. Dedicated database:
A straightforward approach where each tenant has its own database. Each tenant has its own set of data that remains logically isolated from data that belongs to all other tenants.

2. Dedicated table and different schema:
Serving multiple tenants under same database, where each tenant has its own sets of tables grouped with schema as required by tenant.

3. Shared Table/Schema:
This approach involves using the same database and the same set of tables to host multiple tenants’ data. A given table can include records from multiple tenants stored in any order; a Tenant ID column associates every record with the appropriate tenant. Any application accessing the row must refer to this column in every query to ensure that one tenant is not able to see another tenant’s data.