Grokking Node.js Design Patterns for Interviews/

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Build a Multi-Tenant Service Factory

Build a Multi-Tenant Service Factory

Create a factory that dynamically selects a service implementation based on tenant ID and service name.

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Problem statement

You’re building a SaaS platform with multiple tenants. Each tenant can override specific services, such as Logger, Auth, or Mailer. Your system holds a global service registry structured like this:

const serviceRegistry = {
  acme: {
    Logger: class AcmeLogger {
      log(msg) {
        return `Acme log: ${msg}`;
      }
    }
  },
  default: {
    Logger: class DefaultLogger {
      log(msg) {
        return `Default log: ${msg}`;
      }
    },
    Auth: class DefaultAuth {
      login(user) {
        return `Default login for ${user}`;
      }
    }
  }
};
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