Single-tenant vs Multi-tenant vs Multi-single-tenant

TL;DR

• Single-tenant: the infrastructure serves a single tenant.
• Multi-tenant: the infrasturcture serves multiple tenants, but there's no isolation (e.g. the same backend server may server multiple tenants, and the database may store data of multiple tenants).
• Multi-single-tenant: a single system runs multiple, individually-provisioned instances to serve multiple different tenants. The computing resources, data storages are isolated from each other.

An analogy: imagine you are a real estate developer

• Single-tenant: you only build one single house for one single customer, and you only serve this one family.
• Multi-tenant : you are building an apartment building, everyone lives in the same building, but in separate apartments.
• Multi-single-tenant: you are building a community of single family houses, each customer having their own separate house.

Single-tenant

Single-tenant: dedicated instance and resources serving only one customer.

For example, you run a database instance just to be used by yourself.

Single-tenant is not really a viable SaaS option.

Multi-tenant:

Multi-tenant: a single instance of software serves multiple customers (tenants), sharing resources.

For example, a database service serving multiple customers; if one customer used up all the resources, all the other customers will be impacted.

Pros:

• Lower Cost: serving hundreds or thousands of customers with one set of infrastructure.
• Easier Maintenance: only one instance to maintain.
• Easier to Scale: onboarding a new customer is as simple as adding a new entry to the tenants table in your database.
• Efficient Resource Utilization

Cons:

• Noisy Neighbor: Because tenants share resources (CPU, database connections), one tenant experiencing a massive, unexpected traffic spike can potentially degrade performance for all other tenants on the same infrastructure.

Multi-single-tenant

Multi-single-tenant: a service have multiple customers, but each customer has its own instance and resources.

For example, a database service serving multiple customers, but each customer has its own instance and dedicated resources; different customers are isolated.

Pros:

• Isolation: the primary benefit. Customers are fully isolated from each other.
• High Degree of Customization & Flexibility
• Easier to Meet Specific Compliance Needs

Cons:

• Higher cost and higher maintenance.
• Inefficient Resource Utilization.
• Slower Onboarding: each new customer requires provisioning new infrastructure and deploying and configuring applications.