1 / 5 Redundancy, Failover & Availability

The Lonely Box

A stack looks like this: a CDN in front, a managed load balancer replicated across three availability zones, four stateless app servers, and one primary Postgres instance whose only protection is a nightly dump to object storage. Which component is the single point of failure?

A

The app tier, because four servers cannot absorb the load if one of them dies

B

The load balancer, because every request in the system passes through one endpoint

C

The Postgres primary, because losing it halts reads and writes until a restore finishes

D

The CDN, because a cache miss sends the request through to the origin servers