The Client-Server and Peer-to-Peer Paradigms

When to Employ This Paradigm

For traditional applications that have centralized services, such as web or mobile clients communicating with backend APIs.
For systems exploring decentralized or "offline-first" capabilities that rely on peer-to-peer synchronization.
To formally document trust boundaries, client-server version negotiation, and API evolution strategies.

Systems with no network boundary between UI and logic (use archetypes:architecture-paradigm-modular-monolith)
Choosing among paradigms in the first place (use archetypes:architecture-paradigms)

Define Responsibilities: Clearly delineate which logic and data reside on the client versus the server, with the goal of minimizing duplication.
Document the Contracts: Formally document all APIs, data schemas, authentication flows, and any capability negotiation required for handling different client versions.
Plan for Version Skew: Implement a strategy to manage different client and server versions, such as using feature flags, Accept headers for content negotiation, or semantic versioning for APIs.
Address Connectivity Issues: If the application is not purely client-server, design for intermittent connectivity. This may involve implementing offline caching, data synchronization protocols, or peer discovery and membership services.
Secure All Communications: Enforce the use of TLS for all data in transit. Implement authorization policies, rate limiting, and detailed telemetry for every endpoint.