Design a multi-tenant course purchase and delivery system

Design a multi-tenant online course purchasing and delivery system with the following requirements.

Domain model / requirements

• There are multiple Companies (tenants).
• Each company has multiple Organizations .
• Each organization has multiple Members .
• The platform hosts multiple Courses .
• Each course can have prerequisites (other courses) that must be completed/owned before access.
• Pricing differs by company depending on the company’s purchased plan/contract (same course may have different prices for different companies).
• A company can buy courses on behalf of members inside an organization (e.g., assign seats/licenses).
• New companies, organizations, and members may be created at any time.
• Every member must have a system-wide unique Member ID .
• You are given (or can assume existence of) a class definition object for a course and a function to query a course’s prerequisites.

What to design

1. Core APIs (creating companies/orgs/members, browsing courses, purchasing, assigning entitlements, checking access).
2. Data model (multi-tenancy, membership, purchases/entitlements, prerequisite representation).
3. High-level architecture and key services.
4. How course access is enforced (including prerequisite checks).
5. Scalability, consistency, and operational concerns (auditing, retries, idempotency).

Assume typical enterprise needs: high read volume for catalog/access checks, strict correctness for purchases, and reasonable latency for prerequisite queries.