Vercel Speed Audit

# Vercel Speed Audit Skill

Optimize Vercel build and deploy speed for any project. Run as a checklist when starting new projects or auditing existing ones.

When to Use

• New project setup — configure optimal defaults from day one
• Build times creeping up — audit and fix performance regressions
• Deploy queue bottlenecks — eliminate waiting on concurrent builds
• Production incidents — use instant rollback instead of waiting for a new build
• Cost optimization — balance speed vs spend on build infrastructure

Triage First (Don't Blindly Run All 10)

Before running the full checklist, measure and assess:

```bash # 1. Check current build times cd <project> && npx vercel ls --limit 5

# 2. Check team/plan tier npx vercel team ls ```

Decision tree:

| Build Time | Action | |-----------|--------| | < 20s | Only do items 0, 1, 3-5, 10. Skip GitHub Actions (#8), skip barrel file audit (#6) unless codebase is large. | | 20-60s | Do items 0-7, 10. GitHub Actions (#8) is optional. | | 60s+ | Do everything. GitHub Actions (#8) becomes high-value. |

Auth-gated app? (All pages behind login) → Skip ISR (#9) entirely. ISR caches one response for all users — incompatible with per-user content.

Framework: → SvelteKit: Also read `docs/sveltekit.md` — includes adapter-vercel switch, prerendering, $env tips. → Next.js/Nuxt/Other: `docs/general.md` covers framework-agnostic items.

Checklist (Ordered by Impact)

| # | Optimization | Impact | CLI-checkable? | Plan Required | |---|-------------|--------|:-:|:-:| | 0 | Use explicit adapter (e.g., `adapter-vercel` not `adapter-auto`) | Faster, no detection overhead | ✅ Check config | Any | | 1 | Turbo Build Machines | 50-70% faster builds | ❌ Dashboard only | Pro+ | | 2 | On-Demand Concurrent Builds | Eliminates deploy queue | ❌ Dashboard only | Pro+ | | 3 | Prerender Static Pages | Fewer functions, faster TTFB | ✅ Audit code | Any | | 4 | Ignored Build Step | Skip irrelevant builds | ✅ Check vercel.json | Any | | 5 | Prioritize Production Builds | Prod deploys go first | ❌ Dashboard only | Pro+ | | 6 | Eliminate Barrel Files | 10-30% build speedup | ✅ Audit code | Any | | 7 | Audit & Trim Dependencies | Faster install + bundle | ✅ Run depcheck | Any | | 8 | GitHub Actions + `--prebuilt` | Full cache control, skip Vercel build | ✅ Add workflow | Any | | 9 | ISR for Dynamic Pages | Fewer cold starts | ✅ Audit routes | Any | | 10 | Instant Rollback | Zero-downtime recovery | ✅ `vercel rollback` | Hobby: last only; Pro+: any |

Pro plan items (#1, #2, #5): If not on Pro, check team plan first. These are the highest-impact free wins on Pro.

Dashboard Links (Can't Check via CLI)

• For a team called `<team-slug>`:
• Turbo machines: `https://vercel.com/<team-slug>/<project>/settings` → General → Build Machine
• Concurrent builds: `https://vercel.com/teams/<team-slug>/settings` → Build Queue
• Prioritize prod: `https://vercel.com/<team-slug>/<project>/settings` → Git → Production prioritization

Docs

• docs/checklist.md — Full detailed checklist with how-to for each item
• docs/sveltekit.md — SvelteKit-specific optimizations
• docs/general.md — Framework-agnostic Vercel optimizations
• docs/github-actions-prebuilt.md — GitHub Actions + `vercel deploy --prebuilt` guide

Lessons Learned

Real-world findings from running all 10 checks on a SvelteKit project with 16-18s builds:

1. Half the checklist was overkill — builds were already fast. Triage step now prevents wasted effort.
2. ISR is irrelevant for auth-gated apps — every page served per-user content. Added decision tree.
3. `adapter-auto` → `adapter-vercel` was a missed win — not in original 10 but came up in dep audit. Now item #0.
4. Dashboard-only settings are the highest-impact items (Turbo, concurrent, priority) but can't be verified via CLI. Added direct links.
5. GitHub Actions + prebuilt only worth it at 60s+ — for fast builds, the Vercel Git integration is simpler and equally fast.
6. The dep audit found the project was already lean (11 deps, 84MB node_modules, 472K client bundle). Only one unused dep (clsx).
7. Team/plan tier gates most high-impact items — checking plan should be step 1.

Quick Start

1. Triage: Measure build times + check plan tier
2. Run applicable items from the checklist based on decision tree
3. If SvelteKit, also review `docs/sveltekit.md`
4. Track findings in a report file (e.g., `vercel-speed-report.md`)
5. For complex CI needs, follow `docs/github-actions-prebuilt.md`