DEVOURED
Multi-Tenant CDC: Database-per-Tenant SaaS Architecture Guide
Scaling database-per-tenant SaaS requires a fan-in CDC architecture where each tenant's database is captured individually to prevent cross-tenant key collisions.
What: Brian Sheehan outlines an architecture using Estuary to replicate multiple isolated PostgreSQL tenant databases into shared analytics tables by tagging rows at the source and using composite destination keys.
Why it matters: As SaaS providers grow, the 'database-per-tenant' model offers superior security and failure isolation, but it creates immense operational complexity for analytics; this architecture bridges that gap by unifying data downstream while maintaining segregation upstream.
Takeaway: If building multi-tenant analytics, disable automatic binding discovery to prevent schemas from clashing, and explicitly key your destination tables on both 'tenant_id' and 'primary_key'.
Deep dive
- Each tenant database requires its own PostgreSQL replication slot and dedicated CDC capture process.
- Primary key collisions are avoided by adding a 'source tag' at the capture layer and using a composite key (tenant identifier + primary key) at the destination.
- Scaling is best managed by organizing captures into cohorts based on region, workload, or schema version.
- Log-based CDC avoids the performance pitfalls of repeated polling, but stalls in one capture can hold back the Write-Ahead Log (WAL) for the entire PostgreSQL server.
- Schema changes should be rolled out additively; otherwise, incompatible types will force a full collection reset, impacting all tenants.
- Operational resilience requires careful monitoring of each tenant's replication slot to prevent disk bloat from unconsumed WAL logs.
Decoder
- CDC (Change Data Capture): A set of software design patterns used to identify and track changes in a database so that actions can be taken using the changed data.
- WAL (Write-Ahead Log): A standard method for ensuring data integrity in databases where changes are logged to stable storage before they are applied to the main data files.
- Replication Slot: A mechanism in PostgreSQL that automatically keeps track of the WAL position to ensure that the data is not deleted before the consumer has read it.
- Fan-in: An architectural pattern where data from many distinct sources is aggregated into a single destination or data store.
Original article
Full article content is not available for inline reading.
Explore all 58 articles in today's digest
Fresh dev news, AI-digested daily. Never miss a trend at devoured.fyi