Multi-Tenancy Approach in PostgreSQL

In the age of SaaS and cloud-based services, applications often cater to multiple clients, each with their distinct sets of data. Ensuring data isolation and privacy becomes paramount in this multi-client environment. Historically, multi-tenancy has been a favored design pattern where a single software instance serves multiple customers. However, the traditional approach of creating separate databases for each client to ensure data isolation comes with its own set of challenges:

Database Limitations: Many database systems or hosted DBaaS (Database as a Service) offerings have limitations on the number of databases that can be spun up in a single instance or cluster. This restricts scalability, especially for platforms with a growing user base.

Resource Overhead: Maintaining separate databases for each client can be resource-intensive. Not only does it require more storage, but the overhead of managing, backing up, and monitoring multiple databases also increases.

Operational Complexity: Deploying schema updates or performing data migrations across multiple databases can become complex and error-prone. Ensuring consistency across all client databases is crucial, yet challenging.

Given these constraints, there’s a clear need for a solution that offers data isolation without the overhead of multiple databases. This is where PostgreSQL’s Row Level Security (RLS) emerges as a promising alternative, providing granular data access controls within a single database instance.

What is Row Level Security?

Row Level Security (RLS) lets you define access control policies at the row level within tables. This means that you can specify which users can SELECT, INSERT, UPDATE, or DELETE rows based on the actual data within the row. It’s a granular approach to access control directly at the database layer.

Implementing Multi-Tenancy using RLS

Let’s take the example of a generic table named client with a column client_id that uniquely identifies each client.

CREATE TABLE client (
    client_id PRIMARY KEY,     
    client_name VARCHAR(255) NOT NULL,
    email VARCHAR(255),               
    registration_date DATE DEFAULT CURRENT_DATE…