Non-functional requirements.

also: non-functional requirement · NFRs · NFR · quality attributes

How well the system does its job: latency, availability, throughput, durability, security and compliance targets.

the two-minute refresher

Non-functional = how WELL the system does it: 99.99% uptime, <100 ms latency, 1M requests/s, encryption, GDPR.
They drive the architecture, technology choices, infrastructure size and cost.
Turn vague words into numbers: 'fast' becomes 'P99 under 200 ms'.
Always clarify both kinds: functional says what to build, non-functional says how.

also: non-functional requirement · NFRs · NFR · quality attributes

How well the system does its job: latency, availability, throughput, durability, security and compliance targets.

Non-functional = how WELL the system does it: 99.99% uptime, <100 ms latency, 1M requests/s, encryption, GDPR.
They drive the architecture, technology choices, infrastructure size and cost.
Turn vague words into numbers: 'fast' becomes 'P99 under 200 ms'.
Always clarify both kinds: functional says what to build, non-functional says how.