System Design Review

Priority: P1 (HIGH)

Score against evidence, not intent. A claim with no number or artifact scores zero.

Axis	Scores 10 when	Scores 0 when
Requirements	Functional, NFR, and out-of-scope written with owners	Only a feature description exists
Capacity evidence	Peak QPS, storage, and bandwidth computed and current	Numbers absent or older than the last traffic change
Redundancy	No SPOF; failover drilled with a measured RTO	Single instance or untested failover on a critical path
Data scaling	Access patterns mapped, ownership single, growth path stated	One shared store, no growth plan, unbounded tables
Caching	Hot read paths cached with TTL and invalidation defined	No cache on a proven hot path, or uninvalidatable cache
Async offload	Slow and bursty work queued with drain rate and DLQ	Everything synchronous on the request path
Observability	Traffic, error, latency, saturation instrumented with owned alerts	Logs only, or alerts with no runbook
Rollout	Canary or flag with metric rollback trigger and reversible migrations	Big-bang deploy, irreversible migration
Cost proportionality	Spend is sized to the traffic and the risk, and someone can state it	Topology bought for an imagined scale nobody measured