---
category: reference
tags: [phase-0, benchmarks, infrastructure]
last_updated: 2026-03-13
confidence: high
---

# Phase 0 — EFS Benchmarks

## Summary

All Phase 0 exit criteria pass. Git on EFS via Lambda is viable for the wikibot.io use case.

## Environment

- Lambda: Python 3.12, 512MB memory, VPC-attached (us-east-1a)
- EFS: One Zone (us-east-1a), encrypted, access point at /wikibot
- Git library: dulwich 1.1.0 (pure Python, no binary dependency)
- X-Ray: Active tracing enabled

## Results

### Cold Start (5 invocations, forced via env var update)

| Metric | Value |
|--------|-------|
| Mean | 3,407ms |
| Median | 3,403ms |
| P95 | 3,524ms |
| Min | 3,234ms |
| Max | 3,524ms |

**Target: <5,000ms — PASS**

Cold start breakdown (typical): ~2,400ms VPC ENI attach + ~160ms git init + ~600ms commit + ~2ms read + ~40ms log.

### Warm Read (25 invocations)

| Metric | Lambda time | Wall time (incl. network) |
|--------|-------------|--------------------------|
| Mean | 2.07ms | 272ms |
| Median | 2.02ms | 270ms |
| P95 | 2.46ms | 282ms |

**Target: <500ms wall — PASS**

Wall time is dominated by Lambda invoke overhead (~270ms), not EFS I/O (~2ms).

### Warm Write (25 invocations)

| Metric | Lambda time (init + commit) |
|--------|---------------------------|
| Mean | 247ms |
| Median | 245ms |
| P95 | 284ms |

**Target: <1,000ms — PASS**

### Concurrent Reads (3 simultaneous, 5 rounds)

- 15/15 succeeded, no errors
- Mean wall time: 610ms (includes cold starts in early rounds)
- Median wall time: 337ms (warm)

**PASS — no errors under concurrent read load.**

### Concurrent Writes (5 simultaneous, 3 rounds)

- 5/15 succeeded, 10 failed with git lock contention
- No data corruption observed

**Expected behavior.** dulwich uses file-based locking on the git repo. Concurrent writers are rejected, not queued. In production, writes are serialized through a single API endpoint, so this is not a concern.

## Git Library Decision

**dulwich** (pure Python) over gitpython (shells out to `git` binary).

Rationale:
- Lambda Python 3.12 runtime does not include the `git` binary
- Bundling git would add ~30MB and require a Lambda layer or container image
- dulwich works with both bare and non-bare repos via its object API and porcelain API
- 39MB total package size (dulwich + aws-xray-sdk) — well within Lambda limits

## Implications for Phase 1

- VPC cold starts (~3.4s) exceed the Core Web Vitals LCP "good" threshold of 2.5s. A cold-start page load in the web UI would score "poor" by LCP standards. Provisioned Concurrency ($10-15/mo for 1 warm instance) can eliminate this.
- EFS I/O is fast (~2ms read, ~250ms write including git commit). Not a bottleneck.
- The ~270ms Lambda invoke overhead dominates read latency. This is inherent to VPC Lambda and acceptable for MCP tool calls.
- Concurrent write serialization must be handled at the application layer, not git layer.