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Alex Spinov
Alex Spinov

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Convex Has a Free Backend API — Here's Why Developers Are Ditching Firebase

#convex #backend #database #webdev

What if your database automatically synced with your frontend in real-time — no WebSockets, no cache invalidation, no state management libraries?

That's Convex. And it has a generous free tier.

What is Convex?

Convex is a reactive backend platform that replaces your database, server functions, and real-time infrastructure with a single service. Write your backend in TypeScript, and everything just works.

Why Developers Are Moving to Convex

1. Real-Time by Default 

// This query automatically updates the UI when data changes
import { query } from "./_generated/server";

export const getMessages = query({
  handler: async (ctx) => {
    return await ctx.db.query("messages").order("desc").take(50);
  },
});
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// React component — automatically re-renders on data changes
function Chat() {
  const messages = useQuery(api.messages.getMessages);
  return messages?.map(m => <Message key={m._id} {...m} />);
}
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No WebSocket setup. No polling. No cache invalidation. It just works.

2. ACID Transactions 

import { mutation } from "./_generated/server";
import { v } from "convex/values";

export const sendMessage = mutation({
  args: { body: v.string(), author: v.string() },
  handler: async (ctx, args) => {
    await ctx.db.insert("messages", {
      body: args.body,
      author: args.author,
      timestamp: Date.now(),
    });
    // If this fails, the insert is rolled back automatically
    await ctx.db.patch(userId, { messageCount: count + 1 });
  },
});
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Every mutation is a transaction. No partial writes. No inconsistent state.

3. Type-Safe End-to-End 

// Define your schema
import { defineSchema, defineTable } from "convex/server";
import { v } from "convex/values";

export default defineSchema({
  messages: defineTable({
    body: v.string(),
    author: v.string(),
    timestamp: v.number(),
  }).index("by_timestamp", ["timestamp"]),
});
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Your TypeScript types flow from schema → server functions → client. Change a field name and your IDE catches every reference.

4. Built-in Actions for External APIs 

import { action } from "./_generated/server";

export const analyzeImage = action({
  args: { imageUrl: v.string() },
  handler: async (ctx, args) => {
    // Call OpenAI, Stripe, or any external API
    const result = await fetch("https://api.openai.com/v1/...", {
      body: JSON.stringify({ image: args.imageUrl })
    });
    // Store result in database
    await ctx.runMutation(api.images.saveAnalysis, { result });
  },
});
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5. Scheduled Functions & Cron Jobs 

import { cronJobs } from "convex/server";

const crons = cronJobs();
crons.interval("cleanup", { hours: 24 }, api.cleanup.removeOld);
export default crons;
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Free Tier

Feature Free
Database storage 512 MB
Bandwidth 1 GB/month
Function calls 1M/month
Real-time sync Included
File storage 1 GB

Convex vs Firebase vs Supabase

Convex Firebase Supabase
Real-time Automatic Manual listeners Manual subscriptions
Transactions ACID No transactions SQL transactions
Type safety End-to-end Manual types Via PostgREST
Backend logic TypeScript functions Cloud Functions Edge Functions
Query language TypeScript NoSQL queries SQL

Getting Started 

npm create convex@latest
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That scaffolds a full project. Deploy with:

npx convex dev
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Your backend is live. Changes hot-reload automatically.

The Bottom Line

Convex eliminates the glue code between your frontend and backend. Real-time sync, ACID transactions, and end-to-end type safety — all with a free tier generous enough for side projects and MVPs.

Need custom data solutions? I build web scraping and data extraction tools for businesses. Check out my data tools on Apify or email spinov001@gmail.com for custom projects.

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