# 12 - Performance Workbook

*Purpose* – define **repeatable, data‑driven** benchmarks that guard Stella Ops’ core pledge:  
> *“P95 vulnerability feedback in ≤ 5 seconds.”*

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## 0 Benchmark Scope

| Area             | Included                         | Excluded                  |
|------------------|----------------------------------|---------------------------|
| SBOM‑first scan  | Trivy engine w/ warmed DB        | Full image unpack ≥ 300 MB |
| Delta SBOM ⭑     | Missing‑layer lookup & merge     | Multi‑arch images         |
| Policy eval ⭑    | YAML → JSON → rule match         | Rego (until GA)           |
| Feed merge       | NVD JSON 2023–2025               | GHSA GraphQL (plugin)     |
| Quota wait‑path  | 5 s soft‑wait, 60 s hard‑wait behaviour    | Paid tiers (unlimited)    |
| API latency      | REST `/scan`, `/layers/missing`  | UI SPA calls              |

⭑ = new in July 2025.

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## 1 Hardware Baseline (Reference Rig)

| Element     | Spec                               |
|-------------|------------------------------------|
| CPU         | 8 vCPU (Intel Ice‑Lake equiv.)     |
| Memory      | 16 GiB                             |
| Disk        | NVMe SSD, 3 GB/s R/W               |
| Network     | 1 Gbit virt. switch                |
| Container   | Docker 25.0 + overlay2             |
| OS          | Ubuntu 22.04 LTS (kernel 6.8)      |

*All P95 targets assume a **single‑node** deployment on this rig unless stated.*

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## 2 Phase Targets & Gates

| Phase (ID)            | Target P95 | Gate (CI) | Rationale                              |
|-----------------------|-----------:|-----------|----------------------------------------|
| **SBOM_FIRST**        | ≤ 5 s      | `hard`    | Core UX promise.                       |
| **IMAGE_UNPACK**      | ≤ 10 s     | `soft`    | Fallback path for legacy flows.        |
| **DELTA_SBOM** ⭑      | ≤ 1 s      | `hard`    | Needed to stay sub‑5 s for big bases.  |
| **POLICY_EVAL** ⭑     | ≤ 50 ms    | `hard`    | Keeps gate latency invisible to users. |
| **QUOTA_WAIT** ⭑   | *soft* ≤ 5 s<br>*hard* ≤ 60 s | `hard` | Ensures graceful Free‑tier throttling. |
| **SCHED_RESCAN**      | ≤ 30 s     | `soft`    | Nightly batch – not user‑facing.       |
| **FEED_MERGE**        | ≤ 60 s     | `soft`    | Off‑peak cron @ 01:00.                 |
| **API_P95**           | ≤ 200 ms   | `hard`    | UI snappiness.                         |

*Gate* legend — `hard`: break CI if regression > 3 × target,  
`soft`: raise warning & issue ticket.

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## 3 Test Harness

* **Runner** – `perf/run.sh`, accepts `--phase` and `--samples`.  
* **Metrics** – Prometheus + `jq` extracts; aggregated via `scripts/aggregate.ts`.  
* **CI** – GitLab CI job *benchmark* publishes JSON to `bench‑artifacts/`.  
* **Visualisation** – Grafana dashboard *Stella‑Perf* (provisioned JSON).  

> **Note** – harness mounts `/var/cache/trivy` tmpfs to avoid disk noise.

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## 4 Current Results (July 2025)

| Phase         | Samples | Mean (s) | P95 (s) | Target OK? |
|---------------|--------:|---------:|--------:|-----------:|
| SBOM_FIRST    | 100     | 3.7      | 4.9     | ✅ |
| IMAGE_UNPACK  | 50      | 6.4      | 9.2     | ✅ |
| **DELTA_SBOM**| 100     | 0.46     | 0.83    | ✅ |
| **POLICY_EVAL** | 1 000 | 0.021    | 0.041   | ✅ |
| **QUOTA_WAIT**  | 80      | 4.0*     | 4.9*    | ✅ |
| SCHED_RESCAN  | 10      | 18.3     | 24.9    | ✅ |
| FEED_MERGE    | 3       | 38.1     | 41.0    | ✅ |
| API_P95       | 20 000  | 0.087    | 0.143   | ✅ |

*Data files:* `bench-artifacts/2025‑07‑14/phase‑stats.json`.

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## 5 Δ‑SBOM Micro‑Benchmark Detail

### 5.1 Scenario

1. Base image `python:3.12-slim` already scanned (all layers cached).  
2. Application layer (`COPY . /app`) triggers new digest.  
3. `Stella CLI` lists **7** layers, backend replies *6 hit*, *1 miss*.  
4. Builder scans **only 1 layer** (~9 MiB, 217 files) & uploads delta.

### 5.2 Key Timings

| Step                | Time (ms) |
|---------------------|----------:|
| `/layers/missing`   | 13        |
| Trivy single layer  | 655       |
| Upload delta blob   | 88        |
| Backend merge + CVE | 74        |
| **Total wall‑time** | **830 ms** |

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## 6 Quota Wait‑Path Benchmark Detail

### 6.1 Scenario

1. Free‑tier token reaches **scan #200** – dashboard shows yellow banner.  

### 6.2 Key Timings

| Step                               | Time (ms) |
|------------------------------------|----------:|
| `/quota/check` Redis LUA INCR       | 0.8       |
| Soft wait sleep (server)            | 5 000     |
| Hard wait sleep (server)            | 60 000    |
| End‑to‑end wall‑time (soft‑hit)     | 5 003     |
| End‑to‑end wall‑time (hard‑hit)     | 60 004    |

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## 7 Policy Eval Bench

### 7.1 Setup

* Policy YAML: **28** rules, mix severity & package conditions.  
* Input: scan result JSON with **1 026** findings.  
* Evaluator: custom rules engine (Go structs → map look‑ups).

### 7.2 Latency Histogram

```
0‑10 ms  ▇▇▇▇▇▇▇▇▇▇  38 %
10‑20 ms ▇▇▇▇▇▇▇▇▇▇  42 %
20‑40 ms ▇▇▇▇▇▇     17 %
40‑50 ms ▇           3 %
```

P99 = 48 ms. Meets 50 ms gate.

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## 8 Trend Snapshot

![Perf trend spark‑line placeholder](perf‑trend.svg)

_Plot generated weekly by `scripts/update‑trend.py`; shows last 12 weeks P95 per phase._

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## 9 Action Items

1. **Image Unpack** – Evaluate zstd for layer decompress; aim to shave 1 s.  
2. **Feed Merge** – Parallelise regional XML feed parse (plugin) once stable.
3. **Rego Support** – Prototype OPA side‑car; target ≤ 100 ms eval.  
4. **Concurrency** – Stress‑test 100 rps on 4‑node Redis cluster (Q4‑2025).

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## 10 Change Log

| Date       | Note                                                                    |
|------------|-------------------------------------------------------------------------|
| 2025‑07‑14 | Added Δ‑SBOM & Policy Eval phases; updated targets & current results.   |
| 2025‑07‑12 | First public workbook (SBOM‑first, image‑unpack, feed merge).           |

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