# Stateless KV and Queue Patterns — Guardrails

<details>
  <summary><strong>🧭 Quick Return to Map</strong></summary>

<br>

  > You are in a sub-page of **Cloud_Serverless**.  
  > To reorient, go back here:  
  >
  > - [**Cloud_Serverless** — scalable functions and event-driven pipelines](./README.md)  
  > - [**WFGY Global Fix Map** — main Emergency Room, 300+ structured fixes](../README.md)  
  > - [**WFGY Problem Map 1.0** — 16 reproducible failure modes](../../README.md)  
  >
  > Think of this page as a desk within a ward.  
  > If you need the full triage and all prescriptions, return to the Emergency Room lobby.
</details>


A compact repair guide for serverless and edge stacks that must survive retries, bursts, out-of-order events, and duplicate webhooks. All patterns map back to Problem Map pages with measurable targets.

## When to use this page

* Functions are stateless and scale horizontally.
* You see duplicate side effects on retries or webhook storms.
* Event order is not guaranteed and you must reconcile late arrivals.
* Writes cross multiple systems and need exactly-once semantics in practice.
* You need queues for backpressure without introducing deadlocks.

## Open these first

* Visual recovery map: [rag-architecture-and-recovery.md](https://github.com/onestardao/WFGY/blob/main/ProblemMap/rag-architecture-and-recovery.md)
* Contracts for small, auditable payloads: [data-contracts.md](https://github.com/onestardao/WFGY/blob/main/ProblemMap/data-contracts.md)
* Live ops and tracing: [ops/live\_monitoring\_rag.md](https://github.com/onestardao/WFGY/blob/main/ProblemMap/ops/live_monitoring_rag.md) · [ops/debug\_playbook.md](https://github.com/onestardao/WFGY/blob/main/ProblemMap/ops/debug_playbook.md)
* Boot order and deploy hazards: [bootstrap-ordering.md](https://github.com/onestardao/WFGY/blob/main/ProblemMap/bootstrap-ordering.md) · [deployment-deadlock.md](https://github.com/onestardao/WFGY/blob/main/ProblemMap/deployment-deadlock.md) · [predeploy-collapse.md](https://github.com/onestardao/WFGY/blob/main/ProblemMap/predeploy-collapse.md)
* Storm control pattern: [patterns/pattern\_bootstrap\_deadlock.md](https://github.com/onestardao/WFGY/blob/main/ProblemMap/patterns/pattern_bootstrap_deadlock.md)

## Acceptance targets

* Duplicate side-effects ≤ 0.1 percent across 1 million events.
* P99 queue latency ≤ 5 seconds after backpressure is active.
* Lock contention ≤ 3 percent with P95 wait ≤ 100 ms.
* Exactly-once at the boundary: user-visible action never applied twice even with three retries.
* Audit fields present on every message: `event_id`, `source_id`, `revision`, `index_hash`, `dedupe_key`, `attempt`.

---

## Fix in 60 seconds

1. **Define the dedupe key**
   `dedupe_key = sha256(source_id + revision + index_hash)`
   Store in `kv/done/<dedupe_key> = {ts, status, result_id}` with TTL ≥ max replay window.
   Contract: [data-contracts.md](https://github.com/onestardao/WFGY/blob/main/ProblemMap/data-contracts.md)

2. **Use a leased lock for single-writer sections**
   `kv/lock/<resource>` with value `token` and `ttl = function_timeout - safety_margin`.
   Only the holder token can release. On expiry, another worker may acquire.

3. **Put work behind a queue with visibility timeout**
   Visibility timeout must be greater than `max_processing_time + jitter`. Failed items go to DLQ after `N` attempts. Record `attempt` in the message.

4. **Outbox before publish**
   Write business record and `outbox/<txid>` in the same atomic store.
   A relay process reads the outbox and publishes to the queue.
   Consumers use `inbox/<txid>` as the dedupe ledger.

5. **Idempotent side-effects**
   Before any external call, check `kv/done/<dedupe_key>`.
   If present, return the prior result. If absent, perform the effect then write the ledger.

---

## Typical breakpoints → exact fix

* **Webhook storms and double billing**
  Missing dedupe ledger or TTL too short. Add `kv/done/<dedupe_key>` with long TTL and verify before charge.
  Open: [ops/live\_monitoring\_rag.md](https://github.com/onestardao/WFGY/blob/main/ProblemMap/ops/live_monitoring_rag.md)

* **Queue grows without bound**
  No backpressure or priority lanes. Add consumption quotas per tenant and a high-watermark shed rule.
  Open: [ops/debug\_playbook.md](https://github.com/onestardao/WFGY/blob/main/ProblemMap/ops/debug_playbook.md)

* **Deadlocks when multiple writers compete**
  Locks without leases or cross-locks across resources. Replace with single resource lock per critical section and time-boxed lease.
  Open: [deployment-deadlock.md](https://github.com/onestardao/WFGY/blob/main/ProblemMap/deployment-deadlock.md)

* **Out-of-order events overwrite newer state**
  Apply a monotonic guard: reject if `revision_in_msg < current_revision`. Keep a compaction job to expire stale inbox entries.
  Open: [bootstrap-ordering.md](https://github.com/onestardao/WFGY/blob/main/ProblemMap/bootstrap-ordering.md)

---

## Minimal recipes you can copy

### A) Leased lock with safe release

```txt
acquire(key, ttl):
  token = random()
  ok = kv.setnx("lock/"+key, token, ttl)
  return ok ? token : null

release(key, token):
  if kv.get("lock/"+key) == token:
    kv.del("lock/"+key)
```

### B) Idempotency ledger

```txt
dedupe_key = sha256(source_id + revision + index_hash)

if kv.get("done/"+dedupe_key):
  return replay(kv.get("done/"+dedupe_key))

result = do_side_effect()
kv.set("done/"+dedupe_key, {ts: now(), result_id: result.id}, ttl=30d)
return result
```

### C) Outbox and inbox

```txt
// producer tx
db.begin()
db.insert("orders", row)
db.insert("outbox", {txid, payload})
db.commit()

// relay
for msg in db.scan("outbox"):
  queue.send({txid, payload})
  db.delete("outbox", msg.txid)

// consumer
if kv.get("inbox/"+txid): return
handle(payload)
kv.set("inbox/"+txid, now(), ttl=30d)
```

### D) Token bucket for backpressure

```txt
bucket = "q_tokens/"+tenant
tokens = kv.incrby(bucket, 1, ttl=1s)
if tokens > limit: requeue_with_delay()
```

---

## Observability you must add

* `queue_depth`, `age_of_oldest`, `consume_rate`, `requeue_rate`, `dlq_rate`.
* `lock_acquired`, `lock_conflicts`, `lock_wait_ms_p95`.
* `dedupe_hits`, `double_effects_detected`.
* Trace fields on every event: `event_id`, `dedupe_key`, `attempt`, `tenant`, `route`.

## Verification

* Fire a test that sends the same event 5 times with random delays. Only one side-effect is applied.
* Kill a worker mid-flight. Message becomes visible again and finishes once.
* Reorder by sending `revision=1,3,2`. State ends at 3.
  Open: [eval/eval\_rag\_precision\_recall.md](https://github.com/onestardao/WFGY/blob/main/ProblemMap/eval/eval_rag_precision_recall.md)

## When to escalate

* If locks create long waits or cascades, redesign the critical section into outbox plus eventual reconciliation.
* If queue depth oscillates, split lanes by priority or tenant and apply quotas.
  Open: [ops/live\_monitoring\_rag.md](https://github.com/onestardao/WFGY/blob/main/ProblemMap/ops/live_monitoring_rag.md)

---

### 🔗 Quick-Start Downloads (60 sec)

| Tool                       | Link                                                                                                                                       | 3-Step Setup                                                                             |
| -------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------ | ---------------------------------------------------------------------------------------- |
| **WFGY 1.0 PDF**           | [Engine Paper](https://github.com/onestardao/WFGY/blob/main/I_am_not_lizardman/WFGY_All_Principles_Return_to_One_v1.0_PSBigBig_Public.pdf) | 1️⃣ Download · 2️⃣ Upload to your LLM · 3️⃣ Ask “Answer using WFGY + \<your question>”   |
| **TXT OS (plain-text OS)** | [TXTOS.txt](https://github.com/onestardao/WFGY/blob/main/OS/TXTOS.txt)                                                                     | 1️⃣ Download · 2️⃣ Paste into any LLM chat · 3️⃣ Type “hello world” — OS boots instantly |

---

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### Explore More

| Layer | Page | What it’s for |
| --- | --- | --- |
| ⭐ Proof | [WFGY Recognition Map](/recognition/README.md) | External citations, integrations, and ecosystem proof |
| ⚙️ Engine | [WFGY 1.0](/legacy/README.md) | Original PDF tension engine and early logic sketch (legacy reference) |
| ⚙️ Engine | [WFGY 2.0](/core/README.md) | Production tension kernel for RAG and agent systems |
| ⚙️ Engine | [WFGY 3.0](/TensionUniverse/EventHorizon/README.md) | TXT based Singularity tension engine (131 S class set) |
| 🗺️ Map | [Problem Map 1.0](/ProblemMap/README.md) | Flagship 16 problem RAG failure taxonomy and fix map |
| 🗺️ Map | [Problem Map 2.0](/ProblemMap/wfgy-rag-16-problem-map-global-debug-card.md) | Global Debug Card for RAG and agent pipeline diagnosis |
| 🗺️ Map | [Problem Map 3.0](/ProblemMap/wfgy-ai-problem-map-troubleshooting-atlas.md) | Global AI troubleshooting atlas and failure pattern map |
| 🧰 App | [TXT OS](/OS/README.md) | .txt semantic OS with fast bootstrap |
| 🧰 App | [Blah Blah Blah](/OS/BlahBlahBlah/README.md) | Abstract and paradox Q&A built on TXT OS |
| 🧰 App | [Blur Blur Blur](/OS/BlurBlurBlur/README.md) | Text to image generation with semantic control |
| 🏡 Onboarding | [Starter Village](/StarterVillage/README.md) | Guided entry point for new users |

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