·6 min read

How to create an AI app with Upstash, Next.js and Replicate

Cameron YoungbloodCameron YoungbloodSoftware Developer (Guest Author)

In this article, we will show you how to rate limit a Next.js app using Upstash Redis. We will be rebuilding lofianime.com, an app that generates AI images with a Stable Diffusion model on Replicate. We will focus predominantly on how to implement Upstash rate limiting with a Redis database. You can checkout the original source code for this project on GitHub.

Why use Upstash?

To avoid high API costs incurred from using hosted AI models, it’s imperative that we rate limit our API routes. Upstash provides an SDK that allows us to easily do this.

Getting Started

We will create a Next.js application and deploy it to Vercel. Alternatively, you can clone the lofianime repository from GitHub, or use one-click deployment from the repo's README file.

Project Setup

Create a new Next.js project. Make sure to enable the App Router, and tailwindCSS. We will use Javascript instead of Typescript for sake of simplicity.

npx create-next-app@latest
npx create-next-app@latest

Install @upstash/ratelimit:

npm install @upstash/ratelimit @upstash/redis
npm install @upstash/ratelimit @upstash/redis

Install the Replicate Node SDK:

npm install replicate
npm install replicate

Database Setup

Create a Redis database using the Upstash Console or the Upstash CLI. Copy the UPSTASH_REDIS_REST_URL and UPSTASH_REDIS_REST_TOKEN variables and place them in the .env.local file in the root directory of your Next project.

Replicate AI Setup

Create a Replicate account. Click on your profile icon and select “API Tokens”. Create a new API token and save it in your .env.local file as REPLICATE_API_TOKEN.

Making the API Route

Create a new API route called app/api/ai/route.js. In this route, we will use Upstash Redis to create a rate limit as well as use the Replicate SDK to generate an image.

Your route should look like this:

import { NextResponse } from "next/server";
 
import { Ratelimit } from "@upstash/ratelimit";
import { Redis } from "@upstash/redis";
import Replicate from "replicate";
 
const redis = new Redis({
  url: process.env.UPSTASH_REDIS_REST_URL,
  token: process.env.UPSTASH_REDIS_REST_TOKEN,
});
 
const ratelimit = new Ratelimit({
  redis: redis,
  limiter: Ratelimit.fixedWindow(5, "1440 m"),
});
 
const replicate = new Replicate({
  auth: process.env.REPLICATE_API_TOKEN,
});
 
export async function POST(request) {
  const identifier = "api-route";
  const result = await ratelimit.limit(identifier);
 
  if (!result.success) {
    return NextResponse.json("No generations remaining.", {
      status: 429,
      headers: {
        "X-RateLimit-Limit": result?.limit,
        "X-RateLimit-Remaining": result?.remaining,
      },
    });
  }
 
  const { prompt } = await request.json();
 
  try {
    const output = await replicate.run(
      // This is the ID of the replicate model you are running
      "doriandarko/sdxl-hiroshinagai:563a66acc0b39e5308e8372bed42504731b7fec3bc21f2fcbea413398690f3ec",
      {
        input: {
          prompt: "In the style of HISGH. " + prompt,
          // ... other model parameters
        },
      },
    );
 
    return NextResponse.json(output, {
      headers: {
        "X-RateLimit-Limit": result?.limit,
        "X-RateLimit-Remaining": result?.remaining,
      },
    });
  } catch (error) {
    console.log(error);
    return NextResponse.json("An error occurred. Please try again later.", {
      status: 500,
    });
  }
}
import { NextResponse } from "next/server";
 
import { Ratelimit } from "@upstash/ratelimit";
import { Redis } from "@upstash/redis";
import Replicate from "replicate";
 
const redis = new Redis({
  url: process.env.UPSTASH_REDIS_REST_URL,
  token: process.env.UPSTASH_REDIS_REST_TOKEN,
});
 
const ratelimit = new Ratelimit({
  redis: redis,
  limiter: Ratelimit.fixedWindow(5, "1440 m"),
});
 
const replicate = new Replicate({
  auth: process.env.REPLICATE_API_TOKEN,
});
 
export async function POST(request) {
  const identifier = "api-route";
  const result = await ratelimit.limit(identifier);
 
  if (!result.success) {
    return NextResponse.json("No generations remaining.", {
      status: 429,
      headers: {
        "X-RateLimit-Limit": result?.limit,
        "X-RateLimit-Remaining": result?.remaining,
      },
    });
  }
 
  const { prompt } = await request.json();
 
  try {
    const output = await replicate.run(
      // This is the ID of the replicate model you are running
      "doriandarko/sdxl-hiroshinagai:563a66acc0b39e5308e8372bed42504731b7fec3bc21f2fcbea413398690f3ec",
      {
        input: {
          prompt: "In the style of HISGH. " + prompt,
          // ... other model parameters
        },
      },
    );
 
    return NextResponse.json(output, {
      headers: {
        "X-RateLimit-Limit": result?.limit,
        "X-RateLimit-Remaining": result?.remaining,
      },
    });
  } catch (error) {
    console.log(error);
    return NextResponse.json("An error occurred. Please try again later.", {
      status: 500,
    });
  }
}

Let’s break this code down. We first create a Redis client using the Upstash SDK. We then use that client to create a RateLimit of 5 requests with a fixed window of 1440 minutes, or 24 hours. Then, we create an instance of Replicate for our image generation. Using Next.js route handlers, we define a function to handle POST requests. In this example, we limit all requests for the app. However, by getting an email or IP address, we can rate limit on an individual visitor level. In our POST function, we check if the user has remaining generations. If they have reached their limit, we return a response with a 429 HTTP status code and set the headers with the limit and the remaining amount. If the user does have remaining generations, we grab the prompt from the request and run the Replicate model using the SDK. Then, we return the output of the model with the Upstash Redis limit data in the response headers.

Building the UI

In your app/page.js file, add the following code:

"use client";
 
import { useState } from "react";
import Image from "next/image";
 
export default function Home() {
  const [inputValue, setInputValue] = useState("");
  const [image, setImage] = useState("");
  const [loading, setLoading] = useState(false);
 
  const handleChange = (e) => {
    setInputValue(e.target.value);
  };
 
  const handleSubmit = async (e) => {
    e.preventDefault();
    setLoading(true);
    const response = await fetch("/api/ai", {
      method: "POST",
      body: JSON.stringify({
        prompt: inputValue,
      }),
    });
    const data = await response.json();
    setImage(data?.[0]);
    setLoading(false);
  };
 
  return (
    <main>
      {!image ? (
        <div className="w-1/2 space-y-2 p-10">
          <form onSubmit={handleSubmit} className="flex flex-col">
            <label className="mb-2 block text-gray-600">
              Enter your prompt
            </label>
            <input
              type="text"
              value={inputValue}
              onChange={handleChange}
              className="rounded-md border border-black px-2 py-1"
            />
            <button
              disabled={loading}
              type="submit"
              className="mt-4 w-max rounded-md border border-black px-4 py-1"
            >
              Submit
            </button>
          </form>
        </div>
      ) : (
        <div>
          <Image
            src={image}
            width={600}
            height={600}
            alt="Generated AI Image"
          />
        </div>
      )}
    </main>
  );
}
"use client";
 
import { useState } from "react";
import Image from "next/image";
 
export default function Home() {
  const [inputValue, setInputValue] = useState("");
  const [image, setImage] = useState("");
  const [loading, setLoading] = useState(false);
 
  const handleChange = (e) => {
    setInputValue(e.target.value);
  };
 
  const handleSubmit = async (e) => {
    e.preventDefault();
    setLoading(true);
    const response = await fetch("/api/ai", {
      method: "POST",
      body: JSON.stringify({
        prompt: inputValue,
      }),
    });
    const data = await response.json();
    setImage(data?.[0]);
    setLoading(false);
  };
 
  return (
    <main>
      {!image ? (
        <div className="w-1/2 space-y-2 p-10">
          <form onSubmit={handleSubmit} className="flex flex-col">
            <label className="mb-2 block text-gray-600">
              Enter your prompt
            </label>
            <input
              type="text"
              value={inputValue}
              onChange={handleChange}
              className="rounded-md border border-black px-2 py-1"
            />
            <button
              disabled={loading}
              type="submit"
              className="mt-4 w-max rounded-md border border-black px-4 py-1"
            >
              Submit
            </button>
          </form>
        </div>
      ) : (
        <div>
          <Image
            src={image}
            width={600}
            height={600}
            alt="Generated AI Image"
          />
        </div>
      )}
    </main>
  );
}

Additionally, update your next.config.js file in the root of the directory to look like this:

const nextConfig = {
  images: {
    remotePatterns: [
      {
        protocol: "https",
        hostname: "pbxt.replicate.delivery",
        port: "",
        pathname: "/**",
      },
    ],
  },
};
 
module.exports = nextConfig;
const nextConfig = {
  images: {
    remotePatterns: [
      {
        protocol: "https",
        hostname: "pbxt.replicate.delivery",
        port: "",
        pathname: "/**",
      },
    ],
  },
};
 
module.exports = nextConfig;

Let’s break this code down. We created a simple React form that will submit the user prompt to our API route. When we receive a response, we set a state variable with the image URL and then render the image in the UI. Finally, we updated next.config.js so that we can remotely load images from Replicate. And it works! If we inspect the network tab of the browser developer tools, we can see the rate limit as well as the number of generations remaining in the headers of our API route response. If we reach the limit, the API will return a 429 status code and will not allow us to generate any more images. Congratulations! You just created a Next.js app that generates images with AI that is rate limited using Upstash Redis. Not too bad, right?

Possible Next Steps

There are many enhancements we can add to make this project even better. Here are a few good examples if you’re feeling lucky:

Add authentication and personal rate limiting

As mentioned above, we could add user authentication using a library such as Auth.js that would allow us to rate limit on an individual basis. We can create an identifier by using the user’s email and use this to rate limit:

const identifier = session.user.email;
const result = await ratelimit.limit(identifier);
const identifier = session.user.email;
const result = await ratelimit.limit(identifier);

Make UI updates to show remaining generations

We could also create an API route that calculates how many generations are left for a user. Then, we can fetch that data in the UI to show the user if their limits were exceeded.

import { Redis } from "@upstash/redis";
 
const redis = new Redis({
  url: process.env.UPSTASH_REDIS_REST_URL,
  token: process.env.UPSTASH_REDIS_REST_TOKEN,
});
 
export async function GET(request) {
  // use identifier to get how many generations the user has left for the 24 hour period
  const identifier = session?.user?.email;
  const windowDuration = 24 * 60 * 60 * 1000;
  const bucket = Math.floor(Date.now() / windowDuration);
 
  const usedGenerations =
    (await redis?.get(`@upstash/ratelimit:${identifier}:${bucket}`)) || 0;
 
  const remainingGenerations = 5 - Number(usedGenerations);
 
  // render remainingGenerations in the UI
  return NextResponse.json({ remainingGenerations });
}
import { Redis } from "@upstash/redis";
 
const redis = new Redis({
  url: process.env.UPSTASH_REDIS_REST_URL,
  token: process.env.UPSTASH_REDIS_REST_TOKEN,
});
 
export async function GET(request) {
  // use identifier to get how many generations the user has left for the 24 hour period
  const identifier = session?.user?.email;
  const windowDuration = 24 * 60 * 60 * 1000;
  const bucket = Math.floor(Date.now() / windowDuration);
 
  const usedGenerations =
    (await redis?.get(`@upstash/ratelimit:${identifier}:${bucket}`)) || 0;
 
  const remainingGenerations = 5 - Number(usedGenerations);
 
  // render remainingGenerations in the UI
  return NextResponse.json({ remainingGenerations });
}

About the Author

Cameron Youngblood is a Full Stack Developer at Ampry Software and a contributor to Alpine Codex. lofianime.com Star this project on GitHub

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