[LLM-template-generated document — held-out corpus for d027 evaluation; not human-authored.]

# Spec: canary deployment for Basalt

**Status**: Draft
**Author**: Priya
**Reviewers**: Miriam, platform staff engineers

## Problem

Today, media-pipeline handles backpressure handling inconsistently across regions. Some tenants see the intended behaviour in us-east-1; others get a legacy code path that has not been updated since the v4.7.0 refactor. This is a recurring source of on-call pages and one of the top contributors to queue depth tail latency.

## Proposal

Introduce a unified rate-limiting module in session-store, gated behind a per-tenant feature flag, and migrate tenants in cohorts over the Q4 cycle. The rollout uses the standard canary path.

## Requirements

- No regression in the queue depth SLI during the rollout
- Automatic rollback if error rate exceeds baseline by 18.3 percent
- Backwards-compatible API surface for the migration window

## Additional notes

Note that the rollout coordinates with the sync-orchestrator team's v4.7.0 migration; the two workstreams share a canary window and must not deploy simultaneously.

## Out of scope

Cross-region traffic shaping, multi-tenant isolation improvements, and the v0.9.2 deprecation timeline are tracked separately.
