Challenges with multitenant architecture choices:

Between single-tenancy and multitenancy, the challenges are different and somewhat more complex. A few are listed below and called out for their specificity. The architectural choices in terms of application and databases are:

AD- a dedicated application server is running for each tenant, and therefore, each tenant receives a dedicated application instance.

AS – a single application server is running for multiple tenants and each tenant receives a dedicated application instance.

AI – a single application server is running for multiple tenants and a single application instance is running for multiple tenants.

DD – a dedicated database server is running for each tenant and therefore the database is also isolated.

DS – a single database server is running for multiple tenants and each tenant gets an isolated database.

DB – a single database server and a single database is being used for multiple tenants

DC – a single database server is running for multiple tenants and data from multiple tenants is stored in a single database and in a single set of tables with same database schema, but separation based on records.

1.       Sharing of resources and higher than average hardware utilization, performance may be compromised. It must be ensured that all tenants get to consume resources. If one tenant clogs up resources, the performance of all other tenants may be compromised. This is specific to multitenancy and not single tenancy.  In a virtualized instances situation, this problem is solved by assigning an equal amount of resources to each instance. The solution may lead to very inefficient utilization of resources and may not suit all multitenant systems.

2.       Scalability: When tenants share the same application and database, scalability suffers. An assumption with single-tenancy is that tenants do not need more than one application or database but there are no such limitations that exist when placing multiple tenants on one server. Tenants from various geographies can use the same application which affects its scalability. In addition, geographies pose constraints, legislations and regulations. For example, EU mandates that invoices sent from within the EU must be stored within the EU. Additional constraints can be brought by tenant to place all the data on the same server to speed up queries.

3.       Security: When security is compromised, the risk for data stealing is high. In a multitenant environment, a security breach can result in the exposure of data to other, possibly competitive tenants. Data protection becomes an important challenge to tackle.

4.       Zero-downtime: Introducing new tenants or adapting to changing business requirements of existing tenants brings along the need for constant growth and evolution of a multi-tenant system.