In system design, redundancy is resilience, and SPOF—Single Point of Failure—is its arch-nemesis.

A SPOF is any individual component of a system that, if it fails, causes the entire system to go down. It’s the load balancer with no failover, the monolithic database with no replica, the EC2 instance that runs everything—alone.

Even in distributed systems, where we aim for high availability, SPOFs still lurk:

  • A single centralized cache layer (e.g., Redis) with no HA setup

  • DNS misconfiguration—yes, your whole stack can fall with that

  • A CI/CD pipeline bound to one region or one engineer's access

The irony? SPOFs are often born out of early optimization or technical debt disguised as speed.

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  • Breaking down why systems fail

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