What is Convex Database?

If you try to explain Convex to a backend engineer, they might get confused. "Is it a database? Is it a backend? Is it a cache?"

It is all three.

Convex is a managed backend platform designed for one specific goal: Global State Synchronization.

The "Aha!" Moment

In a traditional app (Next.js + Postgres), the data flow is:

1. Frontend fetches data.
2. Backend queries DB.
3. Frontend caches it.
4. User updates data.
5. Frontend invalidates cache.
6. Frontend re-fetches data.

It's brittle.

In Convex, the flow is:

1. Frontend subscribes to a query.

That's it. When the data changes on the server, Convex pushes the new result to the client automatically. It works exactly like React.useState, but across every user's device simultaneously.

Code Example: A Chat App

Here is how you write a chat backend in Convex. This is the entire backend code:

// convex/messages.ts
import { query, mutation } from "./_generated/server";
import { v } from "convex/values";

// 1. Read messages (Real-time by default!)
export const list = query({
  handler: async (ctx) => {
    return await ctx.db.query("messages").take(100);
  },
});

// 2. Send message
export const send = mutation({
  args: { text: v.string() },
  handler: async (ctx, args) => {
    await ctx.db.insert("messages", { text: args.text });
    // No need to notify anyone. Convex handles it.
  },
});

Because it's "transactional by default," you never have race conditions. If two users send a message at the exact same millisecond, the database handles it perfectly.

Is It Right For You?

YES if you are building:

• Social apps
• Task trackers (like Linear)
• Uber-style apps with live location
• AI apps where the response streams in

NO if you need:

• On-premise hosting (it's cloud-only)
• Direct SQL access (it has its own query language)

VibeFast Pro includes a fully configured Convex setup because for certain types of apps, it feels like cheating.

Build Faster

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