The four nonfunctional requirement pillars
Nonfunctional requirements: the four pillars
what the system must be like, not what it must do
Performance
response time
throughput
p50 / p95 / p99
SLO + SLA
see s2
Reliability
fault vs failure
no SPOF
fault injection
blameless reviews
see s3
Scalability
describe the load
scale up or out
revisit per 10x
minimal complexity
see s4
Maintainability
operability
simplicity
evolvability
reversible change
see s5
security and compliance are out of this book's scope