Cadence Ladder

What this is

The orthogonal dimension to the three-axis API model. Where axes (Adapter / Resource / Agent) answer who an endpoint serves and where it sits, the cadence ladder answers what cadence it runs at. Five tiers — Stream, Change-feed, Daily batch, Bulk window, Reference — cross with three axes to produce a 3×5 grid where every endpoint occupies exactly one cell.

Purpose

Tier metadata is load-bearing for SLAs, alerting, and recovery. Without it, "endpoint" is too coarse a unit — freshness budgets, replay-vs-resync, alert routing, and agent readiness all collapse into binary green/red instead of the five-tier health model real multi-store operators need. The ladder makes tier mismatches die loudly at boot rather than silently at 2 a.m.

Structure

Five tiers, ordered by cadence:

Tier	Cadence	Payload	Failure mode
Stream	ms–sec	bytes–KB	"no heartbeat in N seconds"
Change-feed	min–hour	KB–MB	"lag exceeded" / "queue depth"
Daily batch	daily	MB	"schedule missed" / "checksum diff"
Bulk window	weekly	MB–GB	"didn't land in window" / "row count off"
Reference	monthly+	varies	"version drift"

Each tier has a different protocol fit, failure metric, recovery primitive, alert pattern, and cache strategy. Mixing tiers in one endpoint makes health unmonitorable — a single alert cannot catch both "stream stalled for 10 seconds" and "weekly file didn't land."

Consumers

All 32 services declare a tier per feed via infra-feed-tier-contract config schema
All agents declare consumes/produces with expected_tier matching the registry — boot-time mismatch is fatal
Brain wiki Bases query renders five-tier health rollup, not one binary
Ops Dashboard SSE channel emits per-tier state-change events

Sources

Synthesized from a national specialty retailer's ~2011 multi-tier RTI architecture for store↔hub data flow — Service Pulse heartbeat (stream), DDS message-queue polling (change-feed), Windows Event Log + CA UNICENTER alert routing (tier-aware), and Interface Groups taxonomy (5 cadence-suggesting groups). Raw intakes preserved unredacted; this card and downstream artifacts abstract the source.

Routing

cadence-ladder spec (infra-cadence-ladder) → feed-tier-contract SDD (infra-feed-tier-contract) → per-tier cards (tier-stream, tier-change-feed, tier-daily-batch, tier-bulk-window, tier-reference) → per-axis cards (axis-adapter, axis-resource, axis-agent) → endpoint library (Brain/wiki/canary-go-endpoint-library) → microservice contracts (docs/sdds/go-handoff/microservice-architecture.md)