ADR-0014: Latency-aware service routing

Status

Accepted (Phase 9)

Context

Function invocations must find a healthy peer hosting the named service without central load balancers.

Decision

• Maintain a userspace service registry (src/registry.rs): tenant/function → peer instances with latency, headroom, and heartbeat TTL.
• Route by score latency_ms * (1.1 - headroom); failover via route_failover skipping failed peers.
• Heartbeats refresh entries; expired instances drop (self-healing registry).
• Integrate Phase 4 telemetry into autoscaler / traffic shedder for scale and admit decisions.

Honesty — “anycast”

This is userspace peer selection, not IP anycast or BGP. Clients (gateway) pick the best peer; there is no kernel/network anycast address.

Consequences

Docs and CLI must say “lowest-latency peer routing”, not “anycast IP”.