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Cloud Computing · Intermediate

Fault Tolerance

Ability of a system to continue operating without interruption when one or more components fail.

Definition

Fault-tolerant systems have redundant components that take over instantly, so users experience no downtime or data loss. It typically costs more than high availability because redundant capacity must run continuously, for example active-active nodes and synchronous replication.

Example

Aurora storage keeps six copies across three AZs and tolerates loss of two copies without affecting writes.

Exam tip

Fault tolerance implies zero downtime; high availability may tolerate brief failover interruptions.

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