.NET Architecture & System Design Interview Question #13

What is a Single Point of Failure (SPOF)?

Architecture Fundamentals, Scalability, Availability & Performance Junior Beginner

Quick Interview Answer

A Single Point of Failure is a component whose failure can make the entire required service unavailable. It may be an application server, database, network device, authentication service, or another critical dependency.

Detailed Explanation

A Single Point of Failure is a component whose failure can make the entire required service unavailable. It may be an application server, database, network device, authentication service, or another critical dependency.

Removing a SPOF usually requires redundancy plus a working failover mechanism. Merely running two copies does not help if both depend on the same failing resource.

Code Example

Bad:
Client -> App -> Single Database

Improved:
Client -> Load Balancer -> App instances
                         -> HA database setup