Multitenancy
Multitenancy is a software architecture where one instance of the application serves multiple customers. Each customer's data is isolated but shares the same codebase.
What Is Multitenancy? Multi-Tenant vs Single-Tenant Architecture
Example: Salesforce runs one massive database and application that serves millions of companies. Each company sees only their data, but all share the same infrastructure. Benefits: lower infrastructure costs, easier updates (deploy once for all customers), better resource utilization. Drawbacks: security complexity, noisy neighbor problems, customization limits. Alternative: single-tenancy (separate instance per customer).
Examples
Salesforce runs one shared application and database that serves millions of companies at once. Each customer only ever sees their own records, but all of them run on the same underlying infrastructure, which is why Salesforce can ship an update once and have it reach every customer simultaneously.