Database Proxies with Deno
Create efficient database proxies using Deno and Workers to connect to traditional or serverless databases.
Database Proxies with Deno is a free Edge Computing with Cloudflare Workers & Deno lesson on CoddyKit — lesson 3 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Edge Computing with Cloudflare Workers & Deno learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.
What are Database Proxies?
Welcome to our lesson on Deno database proxies! An edge database proxy acts as an intermediary layer between your application (like a Cloudflare Worker) and your database.
Instead of your edge function connecting directly to the database, it talks to the proxy. The proxy then handles the actual database connection.
- Why use them? They centralize connection management, enhance security, and enable data transformation before reaching your database.
Why Deno for Proxies?
Deno is an excellent choice for building these database proxies at the edge. Here's why:
- Native HTTP Server: Deno has a powerful, built-in web server, perfect for handling proxy requests.
- Security Model: Its granular permission system means you explicitly grant network or file access, enhancing security.
- Performance: Deno's fast startup times and efficient runtime make it suitable for responsive proxy services.
- TypeScript First: Built-in TypeScript support helps you write more robust and maintainable code for your proxy logic.
Your First Deno Proxy Server
Let's start by creating a basic Deno HTTP server. This server will listen for incoming requests and respond with a simple message, acting as the foundation for our proxy.
Try running this example:
Deno.serve(async (req) => {
const url = new URL(req.url);
if (url.pathname === "/") {
return new Response("Deno Proxy is running!", { status: 200 });
}
return new Response("Not Found", { status: 404 });
}, { port: 8000 });
console.log("Deno proxy listening on http://localhost:8000");Forwarding Requests to DB
Now, let's modify our Deno proxy to forward incoming requests to a 'mock' database endpoint. In a real scenario, this would be your actual database API or a service that interacts with it.
Here, we use a public JSONPlaceholder API to simulate a database call.
Deno.serve(async (req) => {
// Mock database endpoint (e.g., a public API)
const mockDbApi = "https://jsonplaceholder.typicode.com/posts";
const url = new URL(req.url);
// Construct the target URL for the actual database call
let targetUrl = mockDbApi;
if (url.pathname !== "/") {
targetUrl += url.pathname; // Append path for specific resources
}
const proxyReq = new Request(targetUrl, {
method: req.method,
headers: req.headers, // Pass original headers
body: req.body, // Pass original body
});
try {
const dbResponse = await fetch(proxyReq);
// Add a custom header to indicate proxy processing
const newResponse = new Response(dbResponse.body, dbResponse);
newResponse.headers.set("X-Proxy-By", "Deno");
return newResponse;
} catch (error) {
return new Response(`Proxy Error: ${error.message}`, { status: 500 });
}
}, { port: 8000 });
console.log("Deno proxy forwarding on http://localhost:8000");The Need for Connection Pooling
Database connections are expensive to establish. Serverless functions, like Cloudflare Workers, are often short-lived and stateless. If each Worker instance opens a new connection, you can quickly exhaust database connection limits.
Connection pooling is a technique where a pool of open, reusable database connections is maintained. When a request comes in, a connection is borrowed from the pool instead of creating a new one.
Proxy's Role in Pooling
A Deno database proxy can effectively manage connection pooling. Unlike ephemeral Workers, a Deno proxy (e.g., deployed on Deno Deploy or a persistent server) can be a long-lived process.
This allows it to maintain and manage a pool of database connections, serving multiple requests from various Workers without constantly opening and closing connections. This significantly reduces overhead and improves database performance and stability.
Secure Your Database Proxy
Security is paramount. Your Deno proxy acts as a gateway to your database, so it must be secured:
- Hide Credentials: Never expose raw database credentials in your Worker code. The proxy should store and use these securely.
- Authentication for Proxy: Implement authentication (e.g., API keys, JWTs) for your Workers to access the proxy itself. This ensures only authorized edge functions can send requests.
- Permissions: Deno's explicit permission model helps. Only grant the proxy network access to your database, not arbitrary internet access.
Transforming Data at the Edge
Beyond just forwarding, a Deno proxy can transform data. This means modifying request bodies before sending them to the database or altering responses before returning them to the Worker.
This is useful for adding metadata, filtering sensitive information, or normalizing data formats.
Deno.serve(async (req) => {
const mockDbApi = "https://jsonplaceholder.typicode.com/posts";
const url = new URL(req.url);
let targetUrl = mockDbApi;
// Only transform POST requests for simplicity
if (req.method === "POST") {
let requestBody = await req.json(); // Assuming JSON body
requestBody.processedAt = new Date().toISOString(); // Add a timestamp
requestBody.source = "edge-proxy"; // Add a source identifier
const proxyReq = new Request(targetUrl, {
method: req.method,
headers: {
...req.headers,
"Content-Type": "application/json" // Ensure correct type
},
body: JSON.stringify(requestBody), // Send modified body
});
const dbResponse = await fetch(proxyReq);
return new Response(dbResponse.body, dbResponse);
} else {
// For other methods, just forward
const dbResponse = await fetch(new Request(targetUrl, req));
return new Response(dbResponse.body, dbResponse);
}
}, { port: 8000 });
console.log("Deno proxy with data transformation on http://localhost:8000");Worker to Deno Proxy Flow
How would a Cloudflare Worker interact with this Deno proxy?
The Worker would simply make a standard HTTP fetch request to the Deno proxy's endpoint. If your Deno proxy is deployed on a platform like Deno Deploy, it will have a public URL.
The Worker sends its request, the Deno proxy processes it (e.g., handles pooling, adds security, transforms data), and then forwards it to the actual database, returning the database's response to the Worker.
Deno Proxy Benefits?
Which of the following are benefits of using a Deno-based database proxy at the edge?
Lesson Summary
In this lesson, we explored how to create efficient database proxies using Deno. We learned that Deno's native HTTP server and security model make it ideal for this task.
- We built a basic proxy that forwards requests.
- Understood the importance of connection pooling and the proxy's role in it.
- Discussed securing your proxy and transforming data at the edge.
- Finally, we saw how Cloudflare Workers can interact with such a proxy.
This pattern provides a powerful way to manage database interactions from your edge applications.
Frequently asked questions
Is the “Database Proxies with Deno” lesson free?
Yes — the full text of “Database Proxies with Deno” is free to read here on the web, and the Edge Computing with Cloudflare Workers & Deno course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Edge Computing with Cloudflare Workers & Deno course, upgrade to CoddyKit PRO.
What will I learn in “Database Proxies with Deno”?
Create efficient database proxies using Deno and Workers to connect to traditional or serverless databases. You practise Edge Computing with Cloudflare Workers & Deno with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start Edge Computing with Cloudflare Workers & Deno?
No prior experience is required. Edge Computing with Cloudflare Workers & Deno on CoddyKit is structured for beginners through advanced learners; this is — lesson 3 of 4, so you can start here or from the beginning and move at your own pace.
How long does the “Database Proxies with Deno” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this Edge Computing with Cloudflare Workers & Deno lesson?
Yes. Every Edge Computing with Cloudflare Workers & Deno lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- Workers Sites & Pages
- Frontend Framework Integration
- Database Proxies with Deno
- Server-Side Rendering at the Edge