I Built the Same App Three Times: Bolt.new vs V0 Reality Check

I built a todo app with authentication three different ways: Bolt.new, V0, and by hand. Here's the shit that broke and what actually worked.

Bolt.new: The \"Just Make Everything\" Approach

Bolt.new tries to generate complete apps from one prompt. Sometimes it works, sometimes you get absolute garbage. Built by StackBlitz, it's essentially a wrapper around their WebContainer technology that can run Node.js in the browser.

What I tested: "Build a todo app with user authentication and task sharing"

Result: Got a working React app with a Node.js backend in about 4 minutes. But here's the catch - the generated code had some weird choices:

• Used MongoDB with deeply nested objects for simple todos (seriously, why does "task_title" need 4 levels of nesting?)
• Authentication was basic but functional (just JWTs, no refresh tokens)
• The frontend looked like ass but everything connected properly using Express.js
• Database connection had no retry logic (crashed if Mongo hiccupped)

Real deployment reality: Had to spend 2 hours fixing the database schema design and adding proper error handling before I'd trust it in production. The "10 minutes to MVP" claim is bullshit unless you're okay with code that falls over under real load.

Token economics pain: Hit the rate limit after 6 iterations trying to fix the auth flow. Each "regenerate this component" burns through tokens fast - went from free to $20/month real quick. Learned this the hard way when debugging session expiration at 11pm.

V0: The \"Pretty But Incomplete\" Tool

V0 generates gorgeous UI components but leaves you to wire everything together yourself. Note: V0 migrated from v0.dev to v0.app in August 2025, becoming more agentic and targeting non-technical users. Built by Vercel, it uses their ShadCN/UI design system and focuses purely on React frontend components.

What I tested: Same todo app prompt

Result: Got beautiful React components that looked professional as hell. But:

• No backend whatsoever (obviously) - you need your own API
• Had to manually connect to my own REST API
• Components assumed specific TypeScript interfaces that didn't match my backend
• Spent 3 hours figuring out state management between generated components using Zustand
• The Tailwind CSS was perfect but the TypeScript types were sometimes wrong

Integration hell: The generated components are gorgeous but they're built for V0's sandbox, not real apps. Connecting them to actual data required rewriting a bunch of prop interfaces and understanding component composition.

The Vercel lock-in: If you're not deploying to Vercel, you lose half the benefits. The "seamless integration" only works if you're all-in on their Next.js ecosystem.

Real Performance Numbers (Not Marketing Claims)

Built the same todo app with both tools, then stress tested them:

Bolt.new generated app:

• Initial load: like 2.3 seconds, maybe 2.5 depending on your connection
• First paint: 1.1s
• Database queries: Inefficient but functional
• Memory usage: 85MB (lot of unused dependencies)
• I think it was around 47 concurrent users before it shit the bed (no connection pooling)

V0 components + custom backend:

• Initial load: 1.8s (cleaner frontend)
• First paint: 0.9s
• Database queries: Optimized (I wrote them)
• Memory usage: 52MB (only imported what I needed)
• Handled 200+ concurrent users fine

Manual build:

• Initial load: 1.2s
• First paint: 0.6s
• Everything optimized for the specific use case
• 43MB memory usage
• Scales properly because I know what I'm doing

When Each Tool Actually Makes Sense

Use Bolt.new if:

• You need a working prototype in under an hour
• You don't know how to build backends
• You're okay with code that needs cleanup before production
• You're building standard CRUD apps (not anything complex)

Use V0 if:

• You already have a backend or know how to build one
• You care about UI/UX and want professional-looking components
• You're deploying to Vercel anyway
• You have time to handle the integration work

Build manually if:

• You need it to actually work in production without surprises
• Performance matters
• You're building anything non-standard
• You want to sleep well at night

Bolt.new's Architecture: Impressive Until It Breaks

What it actually generates: Bolt.new spits out full React apps with Node.js backends. The generated structure looks professional at first glance, but dig deeper and you'll find some weird choices that violate basic best practices.

Real example from my testing: Asked for a "project management app" and got:

• 47 different npm packages (moment.js, date-fns, AND dayjs for a fucking todo app)
• MongoDB schema with nested objects 4 levels deep for simple task data
• Authentication that stores JWTs in localStorage (security nightmare waiting to happen)
• API endpoints that don't validate input properly
• Database queries that would explode with more than 100 tasks (no pagination or indexing)

The good parts:

• Everything connects together without manual wiring
• User authentication actually works (basic, but functional)
• Database setup is automated
• You get a working app in minutes, not hours

The pain points:

• Code follows no consistent patterns (sometimes functional, sometimes OOP, sometimes both in the same file)
• Error handling is either missing or catches everything and logs nothing useful
• Performance optimizations are non-existent
• The generated backend would fail any code review

Real debugging horror story: Spent 3 hours at 2am figuring out why users kept getting logged out every 5 minutes. Turns out Bolt hardcoded the JWT secret as "your-secret-key" and set expiry to 300 seconds. In production. With real user data. The auth flow looked perfect in dev but was a security shitshow.

V0's Component Game: Solid but Incomplete

What it actually produces: V0 generates legitimately good React components. The code quality is significantly higher than Bolt.new's output.

Real example from testing: Asked for a "user profile component" and got:

• Clean TypeScript interfaces that actually match the data structure
• Proper accessibility attributes (aria-labels, proper heading hierarchy)
• Responsive design that doesn't break on mobile using Tailwind breakpoints
• Loading states and error handling built in
• CSS that follows design system principles

The good parts:

• Components work exactly as advertised
• Code is readable and follows React best practices
• TypeScript definitions are accurate
• Styling is consistent and professional
• Easy to customize and extend

The integration nightmare:

• Generated components assume specific data structures
• No backend, so you're building APIs from scratch
• State management between components requires manual work
• Authentication integration is entirely on you
• Deployment needs custom setup (unless you're all-in on Vercel)

Real integration pain: V0 generated a gorgeous data table component that expected { id, name, createdAt } but my API returned { _id, fullName, created_at }. Spent 2 hours writing data transformers and cursing at TypeScript errors. Component was beautiful, the integration made me question my life choices.

Performance Testing: Numbers Don't Lie

Tested both tools building user dashboards with 1000 records:

Bolt.new Performance Issues:

• Loads entire dataset on page load (no pagination)
• Re-renders everything on state changes (no memoization)
• Makes separate API calls for each user avatar (classic N+1 problem)
• Bundle includes unused parts of libraries (2MB+ initial load)
• Memory leaks in onClick handlers (forgot to cleanup event listeners)

V0 + Custom Backend:

• Proper pagination and virtual scrolling
• Optimized re-renders with React.memo
• Single API call with proper data fetching
• Tree-shaking works correctly (700KB bundle)
• No memory leaks (I wrote the backend properly)

The reality: Generated code works for demos but falls apart under real load. You'll spend more time optimizing generated code than you would building it right the first time.

When the AI Gets Confused

Bolt.new failure modes (experienced personally):

• Asked for a "chat app" and got a forum instead
• Requested "user authentication" and got OAuth + JWT + sessions all at once
• Said "make it secure" and it added 6 different validation libraries
• Prompt included "responsive design" and it generated 4 different mobile breakpoints

V0 failure modes (also experienced):

• Asked for a "form" and got individual input components instead of a complete form
• Requested "data visualization" and got a table instead of charts
• Said "make it interactive" and it added click handlers that didn't do anything
• Prompt mentioned "accessibility" and it over-engineered ARIA attributes

The lesson: Both tools are impressive until you need something slightly outside their training data. Then they make bizarre assumptions and generate weird solutions.