Server roles across layers: At which layer can a “server” not serve in a multi-tier application stack from a role perspective?

Introduction / Context:
In multi-tier systems we distinguish client, application (business), and data (database) layers. The term “server” typically denotes a service-providing role rather than the consumer UI.

Given Data / Assumptions:

• Client layer is the consumer (e.g., browser, mobile app).
• Business layer exposes services and logic.
• Database layer stores and serves data.

Concept / Approach:

A server provides resources or services to clients. Therefore, it naturally belongs to the business (application) layer or the database layer. The client layer is a consumer, not a provider, so a “server” does not serve there by definition.

Step-by-Step Solution:

Verification / Alternative check:

Architectural diagrams show load balancers → app servers → DB servers, with user agents (clients) at the edge.

Why Other Options Are Wrong:

Business and Database layers are exactly where servers operate.

“All of the above” contradicts the existence of app/DB servers.

Common Pitfalls:

Confusing physical devices (client machines) with logical roles; calling a heavy desktop “server.”

Final Answer:

Client Layer