modbender 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:
# 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 --prebuiltguide
Lessons Learned
Real-world findings from running all 10 checks on a SvelteKit project with 16-18s builds:
- Half the checklist was overkill — builds were already fast. Triage step now prevents wasted effort.
- ISR is irrelevant for auth-gated apps — every page served per-user content. Added decision tree.
adapter-auto→adapter-vercelwas a missed win — not in original 10 but came up in dep audit. Now item #0.- Dashboard-only settings are the highest-impact items (Turbo, concurrent, priority) but can't be verified via CLI. Added direct links.
- GitHub Actions + prebuilt only worth it at 60s+ — for fast builds, the Vercel Git integration is simpler and equally fast.
- The dep audit found the project was already lean (11 deps, 84MB node_modules, 472K client bundle). Only one unused dep (clsx).
- Team/plan tier gates most high-impact items — checking plan should be step 1.
Quick Start
- Triage: Measure build times + check plan tier
- Run applicable items from the checklist based on decision tree
- If SvelteKit, also review
docs/sveltekit.md - Track findings in a report file (e.g.,
vercel-speed-report.md) - For complex CI needs, follow
docs/github-actions-prebuilt.md