.NET Architecture & System Design Interview Question #14

What is redundancy in system design?

Architecture Fundamentals, Scalability, Availability & Performance Junior Beginner

Quick Interview Answer

Redundancy means providing additional instances, copies, or paths so the system can continue operating when a component fails.

Detailed Explanation

Redundancy means providing additional instances, copies, or paths so the system can continue operating when a component fails.

Examples include multiple application instances, replicated databases, redundant network paths, and multi-zone deployments. Redundancy adds cost and does not guarantee availability unless failures are detected and traffic or responsibility can move to healthy resources.

Code Example

-> App A
Client -> LB -> App B
           -> App C

Multiple instances provide redundancy.