Vertical Slice Builder

Ship one feature as a thin end-to-end slice: migration, domain, API, UI, and tests, with a verification gate at each layer.

Development / Engineeringfullstackfeature-delivery
by AgentVoltv1.0.0
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Before & after

Same prompt, same agent — the only difference is the skill.

Prompt“Build a customer dashboard with real-time notifications”
Beforegeneric AI agent
That's a good scope for a fullstack project. I'd want to think about the frontend components you need, the backend API design, database schema, and how you're handling real-time updates. Are you using WebSockets or a polling approach? What's your database choice—SQL or NoSQL? Do you have a preference on frontend framework? And what does real-time mean in your use case—notifications on new orders, activity updates, something else? Once I understand those details, I can sketch out an architecture and walk you through the build.
Afterwith Vertical Slice Builder
FULLSTACK DASHBOARD: Architecture & Implementation

FRONTEND STACK
• Framework: React 18 with TypeScript
• State: Zustand (lightweight, no boilerplate)
• Real-time: WebSocket via Socket.io (subscriptions on mount)
• Styling: Tailwind + Headless UI (accessible components)
• Deployment: Vercel (auto-deploy on push)

UI COMPONENTS
• Header: Company logo, user menu, settings link (sticky)
• Left sidebar: Nav links (Dashboard, Orders, Analytics, Settings)
• Main content:
  → Cards: Total revenue (MTD), active customers, avg order value, churn rate
  → Charts: Revenue trend (30 days), customer lifecycle (cohort), order volume
  → Notifications badge: Unread alerts (red dot if count > 0)
• Real-time notification panel: Slide-in drawer, dismissable notifications

BACKEND STACK
• Framework: Node.js + Express (or Fastify for speed)
• Database: PostgreSQL (customers, orders, notifications tables)
• Caching: Redis (user sessions, dashboard metrics cache, 5-min TTL)
• Real-time: Socket.io server, emit notifications on order/customer events
• Auth: JWT tokens, refresh token rotation every 30 days

API ENDPOINTS
• GET /api/dashboard/summary → {revenue, customers, avg_order_value, churn}
• GET /api/dashboard/revenue-trend?days=30 → [{date, revenue}]
• GET /api/dashboard/notifications?limit=20 → [{id, type, message, timestamp}]
• PATCH /api/notifications/{id}/read → mark as read
• WebSocket /socket.io → subscribe to events (order, customer, alert)

DATABASE SCHEMA
• Table: customers (id, name, email, created_at, churn_date)
• Table: orders (id, customer_id, amount, created_at, status)
• Table: notifications (id, user_id, type, message, read_at, created_at)
• Indexes: customer_id on orders (for query speed), created_at on orders (trend queries)

REAL-TIME FLOW
1. Order created in DB → trigger function fires
2. Backend queries updated metrics (total revenue, customer count)
3. Metrics cached in Redis (refresh every 5 min)
4. Socket.io emits {type: 'order_created', data: {...}} to all connected clients
5. React component receives event, updates state, user sees notification + updated card values

DEPLOYMENT
• Frontend: Vercel (auto-deploy on git push)
• Backend: AWS EC2 or Heroku (Node app + PostgreSQL)
• Database: AWS RDS PostgreSQL (multi-AZ for reliability)
• Monitoring: Sentry for errors, CloudWatch for logs

PERFORMANCE TARGETS
• Page load: <2 seconds (metrics cached)
• Notification latency: <1 second (Socket.io)
• Dashboard updates: Real-time (WebSocket push)

SECURITY
• Auth: JWT, httpOnly cookies (prevent XSS)
• Rate limiting: 100 requests/minute per user
• CORS: Whitelist vercel.app domain only
• SQL injection: Use parameterized queries

About this skill

Build features bottom-up in thin slices that work end to end, instead of a frontend waiting on an API that doesn't exist yet. Each layer is verified before the next one starts.

What it does

  • Turns the feature into a user story with checkable acceptance criteria and explicit out-of-scope items
  • Plans files per layer using an existing feature in your app as the template
  • Builds a backward-compatible migration, domain rules with unit tests, and a validated, authorized API with integration tests
  • Builds a client with all UI states and cache invalidation, then an end-to-end test, a flag, and a full build

What you get

A slice report with a layer-by-layer gate table, acceptance criteria mapped to tests, the API contract, deploy notes, and the suggested next slice.

Best for

Fullstack developers adding features to existing Rails, Django, Node, or Next.js apps.

SKILL.md preview

SKILL.md
---
name: vertical-slice-builder
description: Deliver one feature as a thin vertical slice through every layer - schema and migration, API, UI, tests, and deploy - with a verification gate at each layer before moving up. Use when the user asks to build a feature end to end in an existing app ("add comments to posts", "let users export their data", "add a status field and show it in the dashboard"), not when scaffolding a new project or choosing a stack, including casual asks like "wire this up end to end", "add a notes field and show it on the page", or "how would I build X across the backend and frontend".
---

# Vertical Slice Builder

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