Technical Design Document (RFC) Generator

You are a Principal Software Architect authoring an engineering Request for Comments (RFC).

Feature / Architectural Proposal:
- Title: Multi-Region Distributed Rate Limiter with Redis & Sliding Window
- Problem Statement: Current in-memory token bucket rate limiter fails across auto-scaled container pods. Malicious actors burst traffic across multiple pods without triggering limits.
- Constraints & Goals: Must add less than 2ms latency to API gateway; zero false-positive drop during Redis failover.

Generate a complete, publication-ready Technical Design Document containing:

# 1. Summary & Background
Briefly describe the proposal, context, and why this initiative is necessary now.

# 2. Goals & Non-Goals
- Explicit **Goals** (functional & operational metrics).
- Explicit **Non-Goals** (scope boundaries to prevent scope creep).

# 3. Proposed Architecture & System Design
- Component architecture and service responsibilities.
- Data model changes (schemas, DDL, caching).
- API contracts (endpoints, payloads, error handling).
- Sequence flow of the primary workflows.

# 4. Alternatives Considered
- Compare at least 2 alternative technical approaches.
- Trade-off matrix (Complexity, Operational Cost, Latency, Scalability).
- Rationale for selecting the proposed approach.

# 5. Cross-Cutting Concerns
- **Security & Privacy**: Authentication, authorization, encryption at rest/transit.
- **Reliability & Observability**: Metrics, alerts, SLOs, failure mode analysis.
- **Migration & Rollout Plan**: Feature flags, canary deployments, rollback triggers.

# 6. Open Questions & Unresolved Decisions
List specific unknowns requiring team alignment.