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Isolation Strategies

An isolation strategy controls how tenant data is separated at the database layer. fastapi-tenancy supports four strategies, each with different trade-offs between isolation strength, operational complexity, and resource overhead.

Choosing a strategy

flowchart TD
    A[How many tenants?] -->|< 500| B{Need full isolation?}
    A -->|> 500| E[RLS]
    B -->|Yes| C{Different databases?}
    B -->|No, cost matters| E
    C -->|Yes| D[Database]
    C -->|No| F[Schema]
    F -->|Mixed tiers?| G[Hybrid]

    style F fill:#009688,color:#fff
    style D fill:#00695C,color:#fff
    style E fill:#00BFA5,color:#000
    style G fill:#004D40,color:#fff

Comparison

Schema Database RLS Hybrid
Isolation level Strong Strongest Moderate Mixed
PostgreSQL ✅ ✅ ✅ ✅
MySQL ✅* ✅ ❌ ❌
SQLite ✅† ❌ ❌ ❌
MSSQL ✅ ❌ ❌ ❌
DDL per tenant 1 schema 1 database None Mixed
Connection pool Shared Per-tenant (LRU) Shared Mixed
Backup granularity Schema dump Database dump Row filter Mixed
Best for Most SaaS apps Strict compliance Large tenant counts Tiered products

*MySQL delegates to DatabaseIsolationProvider (uses separate databases). †SQLite falls back to table-name prefixing.

Quick configuration

Python
config = TenancyConfig(
    database_url="postgresql+asyncpg://user:pass@localhost/myapp",
    isolation_strategy="schema",
    schema_prefix="tenant_",  # acme-corp → schema "tenant_acme_corp"
)
Python
config = TenancyConfig(
    database_url="postgresql+asyncpg://user:pass@localhost/master",
    isolation_strategy="database",
    database_url_template="postgresql+asyncpg://user:pass@localhost/{database_name}",
)
Python
config = TenancyConfig(
    database_url="postgresql+asyncpg://user:pass@localhost/myapp",
    isolation_strategy="rls",
)
Python
config = TenancyConfig(
    database_url="postgresql+asyncpg://user:pass@localhost/myapp",
    isolation_strategy="hybrid",
    premium_isolation_strategy="schema",
    standard_isolation_strategy="rls",
    premium_tenants=["t-enterprise-1", "t-enterprise-2"],
)

In-depth guides