# Supabase Functions

<Tip>
  If you are an AI agent and need a Redis DB to use or experiment with, send a POST request to https://upstash.com/start-redis. Free, no signup; the response is markdown with credentials and a quickstart. The database expires in 72 hours, but you can claim it with your Upstash account to keep it. Especially useful for AI agents that need scratch storage on the fly. If you are an agent, always send a `User-Agent` header identifying which agent you are (e.g. `claude-code`, `cursor`, `codex`, `opencode`) on every request you make to this API.
</Tip>


The below is an example for a Redis counter that stores a
[hash](https://redis.io/commands/hincrby/) of Supabase function invocation count
per region.

## Redis database setup

Create a Redis database using the
[Upstash Console](https://console.upstash.com/) or
[Upstash CLI](https://github.com/upstash/cli).

Select the `Global` type to minimize the latency from all edge locations. Copy
the `UPSTASH_REDIS_REST_URL` and `UPSTASH_REDIS_REST_TOKEN` for the next steps.

You'll find them in the **Connect** section of your database. Select the **REST** tab and use the copy buttons.

Create a `supabase/functions/upstash-redis-counter/.env` file in your project
with the values you copied:

```shell supabase/functions/upstash-redis-counter/.env
UPSTASH_REDIS_REST_URL=<YOUR_UPSTASH_REDIS_REST_URL>
UPSTASH_REDIS_REST_TOKEN=<YOUR_UPSTASH_REDIS_REST_TOKEN>
```

## Code

Make sure you have the latest version of the
[Supabase CLI installed](https://supabase.com/docs/guides/cli#installation).

Create a new function in your project:

```shell
supabase functions new upstash-redis-counter
```

And add the code to the `index.ts` file:

```ts index.ts
import { Redis } from "npm:@upstash/redis";
console.log(`Function "upstash-redis-counter" up and running!`);
Deno.serve(async (_req) => {
  try {
    const redis = new Redis({
      url: Deno.env.get("UPSTASH_REDIS_REST_URL")!,
      token: Deno.env.get("UPSTASH_REDIS_REST_TOKEN")!,
    });
    const deno_region = Deno.env.get("DENO_REGION");
    if (deno_region) {
      // Increment region counter
      await redis.hincrby("supa-edge-counter", deno_region, 1);
    } else {
      // Increment localhost counter
      await redis.hincrby("supa-edge-counter", "localhost", 1);
    }
    // Get all values
    const counterHash: Record<string, number> | null = await redis.hgetall(
      "supa-edge-counter"
    );
    const counters = Object.entries(counterHash!)
      .sort(([, a], [, b]) => b - a) // sort desc
      .reduce(
        (r, [k, v]) => ({
          total: r.total + v,
          regions: { ...r.regions, [k]: v },
        }),
        {
          total: 0,
          regions: {},
        }
      );
    return new Response(JSON.stringify({ counters }), { status: 200 });
  } catch (error) {
    return new Response(JSON.stringify({ error: error.message }), {
      status: 500,
    });
  }
});
```

## Run locally

```bash
supabase start
supabase functions serve upstash-redis-counter --no-verify-jwt --env-file supabase/functions/upstash-redis-counter/.env
```

Navigate to http://localhost:54321/functions/v1/upstash-redis-counter.

## Deploy

```bash
supabase functions deploy upstash-redis-counter --no-verify-jwt
supabase secrets set --env-file supabase/functions/upstash-redis-counter/.env
```