Pin the perf framework. Front-end metrics tracked at Google Core Web
Vitals 'Good' thresholds (LCP <= 2.5s, INP <= 200ms, CLS <= 0.1, plus
TBT <= 200ms, TTFB <= 800ms) and Lighthouse Performance >= 90 on
critical routes. Lighthouse CI (@lhci/cli) enforces them in CI with
median-of-3 runs to mitigate runner variance, on a curated
critical-routes list (login, home, accessibility statement, flagship
features as they land). Wires into the perf gate slot from ADR-0015.
Bundle budgets enforced at nx build via Angular's project.json budgets
array, type 'error': initial <= 300 KB gzip, lazy chunks <= 100 KB
gzip, per-component CSS <= 6 KB. source-map-explorer wired as an Nx
analyze target for diagnosis on budget breaches.
Back-end SLOs documented per endpoint family (p95/p99) and observed
via the OpenTelemetry spans already shipped by ADR-0012 - advisory in
CI (load profile unrepresentative), alerting in production. Quarterly
review tightens budgets when achievable.
Scheduled weekly Lighthouse run on the prod env via the existing
security-scheduled.yml workflow extends coverage beyond PR-time.
Explicit a11y/perf trade-off rule: when they conflict, a11y wins (per
APF's mission, ADR-0016). The perf budget is then re-evaluated at the
next quarterly review.
No browser-side RUM SDK in v1 - the OTel browser tracing from ADR-0012
plus scheduled prod Lighthouse runs cover the gap. RUM revisited in
v2 if a real incident escapes the existing signal.
decisions/README.md index updated. CLAUDE.md gains an explicit
'Performance budgets' line pointing to ADR-0017.
Julien Gautier