Designing a scalable system for reciprocal memberships program

Hi everyone,

I’m currently working on designing a digital membership system using Elixir/Phoenix for organizations that offer reciprocal benefits across multiple institutions.

The primary use case revolves around:

Museum reciprocal membership programs

Zoo reciprocal membership networks

Botanical garden reciprocal membership systems

In these models, a member of one institution can access benefits such as free or discounted entry at partner organizations. While the concept sounds straightforward, implementing it at scale brings several technical and architectural challenges.

Here are some of the key problems I’m trying to solve:

1. Distributed Membership Validation
   Each institution maintains its own member database. What would be the best way to validate a member across partner systems?

A. Centralized API?

B. Federated identity approach?

C. Token-based validation?

2. Real-Time Access Verification
   At entry points (like ticket counters), validation needs to be instant.
   Would QR-based systems with signed tokens work better, or should this rely on live API calls?

3. Complex Benefit Rules
   Different partners may offer different levels of access (e.g., free entry, discounts, blackout dates).
   What’s the best way to model and manage these dynamic rules efficiently?

4. Scalability & Fault Tolerance
   If hundreds of museums, zoos, and botanical gardens are connected, the system needs to handle:

High request volumes

Network failures between institutions

Data consistency challenges

I’m particularly interested in how Elixir’s concurrency model and the BEAM ecosystem can help in building a fault-tolerant and highly available system for this use case.

5. Security Considerations
   Preventing misuse of reciprocal memberships is critical.
   What are best practices for:

Preventing duplicate usage

Securing QR codes or digital passes

Handling revoked or expired memberships in real time?

If anyone has worked on similar distributed systems, membership platforms, or access-control solutions in Elixir (or even other stacks), I’d really appreciate your insights.

Also open to suggestions on architecture patterns, libraries, or real-world case studies that could help guide this implementation.

Additionally, I’m exploring how this entire system could be extended into a seamless digital membership card experience (for example, mobile wallets or app-based access), so any input around that would be really helpful as well.