Non-functional requirements

How this question breaks down

1. 1AvailabilityCore18 minAvailability is the share of valid requests a service answers correctly and in time; nines turn that share into a downtime allowance, and redundancy and fast repair are how you buy more of them.
2. 2LatencyCore22 minLatency is a distribution, not a number. Percentiles describe what most users and the unluckiest users feel, and fan-out turns one server's rare slowness into a common one.
3. 3DurabilityCore21 minDurability is the promise that data you acknowledged survives disks, machines, sites and people; where you send the acknowledgement decides which of those failures can lose it.
4. 4ScalabilityCore18 minA system scales when adding machines adds proportional capacity while latency stays inside its target; contention and coordination are what bend the curve.
5. 5SLOsCore20 minAn SLI measures what users feel, an SLO sets a target for it over a window, and the error budget left over decides when to ship faster and when to stop and fix.

Work through the parts in order and you’ve covered the full design. Each part is one topic.