← System Design learning pathSystem Design · Module 8 of 10
Reliability and availability
Keep systems running when parts fail.
📖 Key ideas
- Redundancy: multiple instances across zones/regions.
- Failover switches to backups automatically.
- Timeouts, retries with backoff, circuit breakers.
- Rate limiting and graceful degradation protect core features.
- Backups and disaster recovery plans (RTO/RPO).
💡 Real-life example: Reliability is a hospital's backup generator: when power fails, critical machines keep running.
RedundancyDuplicate components for backup
FailoverSwitching to a standby
Circuit breakerStops calling failing services
Graceful degradationReduced functionality instead of total failure