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Availability –
Formula: uptime / (uptime + downtime)
- SLO (Service Level Objective) – Target uptime (e.g., AWS “five 9s” = 99.999%).
- SLA (Service Level Agreement) – Contractual guarantee; failure triggers compensation (e.g., AWS guarantees 99.9%).
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Key Reliability Umbrella Terms
- Reliability – Probability the service will run without failure.
- Fault Tolerance – Ability to keep working despite component failures.
- Redundancy – Extra capacity or servers (e.g., horizontal scaling).
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Throughput – Requests processed per time unit.
- QPS (Queries Per Second) – Common in server-to-storage operations (CRUD).
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Latency – Time to complete a request.
- Not limited to networking — CPUs use caching to reduce latency and boost performance.