Blue-Green Switchovers for Serverless and Edge

A safe pattern to shift 100 percent of live traffic from blue to green without downtime, cache poison, or state skew. Works for API Gateway + Lambda, Cloudflare Workers, Vercel Edge, Fastly Compute, and similar stacks.

Open these first

Visual map and recovery: RAG Architecture & Recovery
End to end retrieval knobs: Retrieval Playbook
Snippet trace and contracts: Retrieval Traceability · Data Contracts
Meaning vs distance: Embedding ≠ Semantic
Collapse diagnostics: Context Drift · Entropy Collapse · Logic Collapse
Cloud companions: Cold Start & Concurrency · Timeouts & Streaming · Stateless KV & Queues · Edge Cache Invalidation · Runtime Env Parity · Egress & Webhooks · Pricing vs Latency · Secrets Rotation · Multi-Region Routing · Region Failover Drills · Observability and SLO · Canary Release

Core acceptance to flip colors

ΔS(question, retrieved) median ≤ 0.45 on gold probes.
Coverage ≥ 0.70 to correct section.
λ convergent across three paraphrases and two seeds.
p95 warm latency within 25 percent of blue.
Zero new error class at headers or body read.
Cache hit rate within five points once namespaces are split.
INDEX_HASH, metric, analyzer match between blue and green or are intentionally versioned.

Topologies that work

Edge weight switch

One CDN route, two origins. Blue and green behind a weight.
Keep sticky hashing by stable_user_id so dialogs do not jump during ramp.

Header based switch

Default to blue. Send x-exp: green for selected cohorts.
Propagate header to core services and logs.

DNS label switch

api-blue.example.com and api-green.example.com.
Edge forwards based on label. Use short TTL only after green passes probes.

Pre-flight checklist

Env parity proved with the parity sheet. Open: Runtime Env Parity
Secret bundles rotated with overlap. Open: Secrets Rotation
Index family built and labeled: docs-v3-green, analyzer and metric recorded.
Cache namespaces isolated: blue: vs green: prefixes at edge and core.
Queue topics duplicated: jobs.blue and jobs.green. Producers switch at flip time with idempotent keys. Open: Stateless KV & Queues
Probe set ready: 50 to 200 questions, three paraphrases, two seeds.

Switch playbook

Shadow validate Replay a sample to green. Block promotion if ΔS ≥ 0.60, coverage < 0.70, or JSON schema violations.
Canary ramp Move one percent of sticky users to green at the edge. Keep cache namespaces split. Open: Canary Release
Green warmup Ensure cold start panels are flat. If p95 warm is worse only due to cold, fix memory or reserve concurrency. Open: Cold Start & Concurrency
Cutover window
- Freeze new blue writes that create cross request state.
- Drain blue job queues with a backfill guard.
- Switch producers to jobs.green.
- Flip traffic weight to green. Keep blue read only for a short fence window.
Cache migration
- Invalidate user facing keys on the blue prefix.
- Prime green with popular keys. Open: Edge Cache Invalidation
Post cutover audit
- Compare ΔS, coverage, λ, p95 warm to pre-flip baselines.
- Verify INDEX_HASH and analyzer match.
- Confirm egress success rate and dedupe guard. Open: Egress & Webhooks
Decommission blue
- Stop accepting writes.
- Keep blue for rollback until probe board stays green for one peak hour.

Data and state guidance

Databases Prefer live backward compatible migrations. If you need forward only, pause blue writes to the affected tables during the flip.
Vector indexes Version by family. Never point green to blue vectors by accident. Verify metric and analyzer, not only the hash.
Queues and schedulers Idempotent keys: sha256(source_id + revision + index_hash). Keep retry policies aligned across colors.
Caches Always split prefixes. Never reuse the blue prefix for green.

Observability fields to join on

{
  "ts": "2025-08-28T04:00:00Z",
  "route": "chat.rag.answer",
  "color": "green",
  "sticky": "h21",
  "region": "eu-west",
  "edge_pop": "cdg",
  "INDEX_HASH": "0x9a77",
  "retrieval": { "metric": "cosine", "analyzer": "bilstem", "ΔS_q_r": 0.36, "coverage": 0.74, "λ_state": "<>" },
  "cache": { "prefix": "green:", "hit": true },
  "status": 200,
  "latency_ms": { "tffb": 140, "tusable": 320, "tfinal": 1180 }
}

Rollback cookbook

ΔS rises or coverage drops Repoint traffic to blue, keep green read only. Rebuild index with the chunking checklist. Open: Embedding ≠ Semantic · Chunking Checklist
Latency spike at body read Increase memory or reserve concurrency. Adjust stream chunk sizes. Open: Timeouts & Streaming
First call after switch fails Check boot order and version skew. Open: Bootstrap Ordering · Pre-Deploy Collapse
Tool loops start Lock tool schemas and timeouts, split memory namespaces. Open: Multi-Agent Problems

Common traps

Mixing cache prefixes so users see stale blue answers after the flip.
DNS TTL set short before green is warm.
Single region green while blue is multi region.
Reranker versions differ between colors.
Secrets rotated on edge but not core.

🔗 Quick-Start Downloads (60 sec)

Tool	Link	3-Step Setup
WFGY 1.0 PDF	Engine Paper	1️⃣ Download · 2️⃣ Upload to your LLM · 3️⃣ Ask “Answer using WFGY + <your question>”
TXT OS (plain-text OS)	TXTOS.txt	1️⃣ Download · 2️⃣ Paste into any LLM chat · 3️⃣ Type “hello world” — OS boots instantly

🧭 Explore More

Module	Description	Link
WFGY Core	WFGY 2.0 engine is live: full symbolic reasoning architecture and math stack	View →
Problem Map 1.0	Initial 16-mode diagnostic and symbolic fix framework	View →
Problem Map 2.0	RAG-focused failure tree, modular fixes, and pipelines	View →
Semantic Clinic Index	Expanded failure catalog: prompt injection, memory bugs, logic drift	View →
Semantic Blueprint	Layer-based symbolic reasoning & semantic modulations	View →
Benchmark vs GPT-5	Stress test GPT-5 with full WFGY reasoning suite	View →
🧙‍♂️ Starter Village 🏡	New here? Lost in symbols? Click here and let the wizard guide you through	Start →

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