Convex Has a Free API You've Never Heard Of

Convex is a reactive backend-as-a-service that gives you a real-time database, server functions, and file storage. Write TypeScript functions, and Convex handles deployment, scaling, and real-time sync to every connected client.

What Makes Convex Special?

• Reactive by default — queries auto-update when data changes
• Free tier — generous limits for side projects
• ACID transactions — full transactional guarantees
• TypeScript throughout — end-to-end type safety
• Built-in file storage — no S3 needed

The Hidden API: Reactive Queries

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

export const list = query({
  args: { channel: v.string() },
  handler: async (ctx, { channel }) => {
    return await ctx.db
      .query('messages')
      .withIndex('by_channel', q => q.eq('channel', channel))
      .order('desc')
      .take(50);
  }
});

export const send = mutation({
  args: { channel: v.string(), body: v.string(), author: v.string() },
  handler: async (ctx, { channel, body, author }) => {
    await ctx.db.insert('messages', {
      channel, body, author,
      createdAt: Date.now()
    });
  }
});

React Integration — Auto-Updating UI

import { useQuery, useMutation } from 'convex/react';
import { api } from '../convex/_generated/api';

function Chat({ channel }: { channel: string }) {
  // This auto-updates when ANY client sends a message!
  const messages = useQuery(api.messages.list, { channel });
  const sendMessage = useMutation(api.messages.send);

  return (
    <div>
      {messages?.map(msg => (
        <div key={msg._id}>{msg.author}: {msg.body}</div>
      ))}
      <button onClick={() => sendMessage({ channel, body: 'Hello!', author: 'me' })}>
        Send
      </button>
    </div>
  );
}

Scheduled Functions & Cron

// convex/crons.ts
import { cronJobs } from 'convex/server';

const crons = cronJobs();
crons.interval('cleanup', { hours: 1 }, 'cleanupExpired');
crons.cron('daily-report', '0 9 * * *', 'sendDailyReport');
export default crons;

Quick Start

npm create convex@latest
cd my-app && npm run dev

Why Teams Choose Convex

A developer shared: "We built a real-time collaborative editor in a weekend with Convex. No WebSocket code, no conflict resolution logic, no caching layer. The reactive queries handle everything — when one user edits, every other user sees it instantly."

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