Multi-Tenant applications: Deep dive into tenant identification strategies

In this blog post, I will provide a comprehensive analysis of various tenant identification strategies, discussing the pros and cons of each approach in detail.

Tenant Identification Strategies

Subdomains

Each tenant is assigned a unique subdomain, such as tenant1.foo.bar or tenant2.foo.bar. The application can determine the tenant based on the subdomain of the incoming request.

Pros:

• Clear separation between tenants for users and developers.
• Minimal changes to application code, as most web frameworks and libraries support subdomain-based tenant identification.
• Improved SEO and branding opportunities.
• Compatibility with reverse proxies and CDNs like Cloudflare.

Cons:

• Requires managing DNS records for each tenant’s subdomain.
• Subdomain enumeration could lead to potential security risks.
• Involves additional SSL certificate management for securing subdomains.

URL Paths

Tenants are identified by a specific path segment in the URL, such as foo.bar/tenant1 or foo.bar/tenant2. The application extracts the tenant identifier from the URL to determine the appropriate tenant.

Pros:

• No need to manage subdomains, as tenants can be hosted under the same domain.
• Easy to implement in most web frameworks and libraries.
• Simplified tenant management with changes only required in the application’s routing configuration.

Cons:

• Potential for tenant identifier collision if not carefully managed.
• Tenant identifier exposed in the URL could lead to security concerns.
• Less optimal for branding and SEO compared to subdomains.

Custom Headers

Tenants are identified by a custom HTTP header sent with each request. This approach requires the client to include the tenant identifier in every API call.

Pros:

• Consistent tenant identification mechanism across all API endpoints, regardless of the URL structure.
• Enhances security, as the tenant identifier is not exposed in the URL.
• Allows for more complex tenant identification logic, such as using multiple headers or combining headers with other identification methods.

Cons:

• Relies on the client to include the tenant identifier in every request.
• Requires additional application logic to validate and process custom headers.
• May not be compatible with certain web services or client applications that do not support custom headers.

JWT Tokens

Tenants are identified using JSON Web Tokens (JWT). The tenant identifier is included in the JWT payload, and the application extracts the tenant information from the token after validating it.

Pros:

• Secure tenant identification mechanism, as JWT tokens can be cryptographically signed and verified.
• Supports additional claims in the JWT payload for granular access control and tenant-specific configuration.
• Reduces the need for separate tenant authentication mechanisms, as the JWT token can also be used for user authentication.

Cons:

• Adds complexity to the authentication and authorization process, requiring JWT token management.
• Token expiration and revocation need to be handled carefully to prevent unauthorized access.
• Requires additional processing overhead for token validation and decryption.

Summary

In this blog post, we explored various tenant identification strategies for multi-tenant applications, including subdomains, URL paths, custom headers, and JWT tokens. Each approach has its unique set of advantages and disadvantages, with trade-offs related to simplicity, security, branding, SEO, and management overhead.

After analyzing each strategy, I have decided to use subdomains for my multi-tenant applications for the following reasons:

1. Simplicity: Subdomains offer a straightforward way to identify tenants, requiring minimal changes to application code and being widely supported by most web frameworks and libraries.
2. Clear Separation: Subdomains provide a logical separation between tenants, making it easy for users and developers to identify the tenant they are working with.
3. Branding and SEO: Unique subdomains for tenants allow them to have a custom-branded presence under the main application domain, which can improve search engine optimization (SEO).
4. Infrastructure Compatibility: Subdomain-based tenant identification works well with reverse proxies and Content Delivery Networks (CDNs) like Cloudflare, enabling better performance and security for the multi-tenant application.

By choosing subdomains as the tenant identification strategy, I can build scalable, secure, and easy-to-manage multi-tenant applications that cater to the needs of various tenants while providing an optimal user experience.