Fly.io vs Deno Deploy for Solo Developers

Quick Comparison

Fly.io Overview

Fly.io deploys Docker containers as Firecracker micro VMs on edge servers across the world. You get full control over your runtime environment. Any language, any framework, any system dependency. Configure your app in fly.toml, deploy via CLI, and your containers run close to users globally.

The platform includes managed Postgres, persistent volumes, private networking between services, and LiteFS for distributed SQLite. The free tier provides 3 shared VMs. Fly.io is flexible enough to host almost anything, from Node.js APIs to Python ML services to Go web servers.

The tradeoff is that you're managing Docker containers. You need a Dockerfile, you need to think about image size, and deployments take a minute or two for the build step.

Deno Deploy Overview

Deno Deploy is a serverless edge platform that runs JavaScript and TypeScript on V8 isolates across 35+ global regions. There's no container to build, no Dockerfile to write, and no cold start to worry about. Push to GitHub, and your code is live worldwide in seconds.

The platform is tightly integrated with the Deno runtime. Frameworks like Fresh and Hono deploy seamlessly. You get Deno KV (a globally distributed key-value store) and Deno Queues for async processing baked into the platform. The free tier includes 100,000 requests per day, which covers most hobby projects and early-stage products.

Deno Deploy is purpose-built for lightweight, fast, globally distributed applications. It's not trying to be everything. It's trying to be the fastest way to deploy TypeScript to the edge.

Key Differences

Runtime model. Fly.io runs full VMs. Your app has its own operating system, file system, and can install any dependency. Deno Deploy runs V8 isolates, which are lighter but restricted. No file system writes, no native binaries, no arbitrary system calls. If your app needs to shell out to FFmpeg or run Python scripts, Fly.io is your only option. If your app is pure TypeScript, Deno Deploy is simpler and faster.

Language support. Fly.io supports anything that runs in Docker. Python, Go, Rust, Ruby, Java, Node, Deno. Deno Deploy only runs JavaScript and TypeScript through the Deno runtime. This is the biggest filter. If you're not building in JS/TS, the decision is already made.

Deployment speed. Deno Deploy wins decisively. No Docker build, no image push, no VM provisioning. Code goes from git push to globally distributed in seconds. Fly.io deployments take 1-3 minutes depending on your image size and build complexity.

Cold starts. Deno Deploy has near-zero cold starts because V8 isolates spin up in milliseconds. Fly.io VMs stay running (no cold start on the free tier), but if you scale to zero and back, startup takes longer. For APIs where response time matters on every request, Deno Deploy's isolate model is faster.

Data layer. Fly.io gives you managed Postgres, persistent volumes, and the ability to run any database in a container. Deno Deploy offers KV (key-value storage) and nothing else natively. If you need SQL, you pair Deno Deploy with an external database like Neon, PlanetScale, or Supabase. This adds another service to manage and another bill to pay.

Pricing structure. Deno Deploy charges per request. Idle apps cost nothing. Fly.io charges per VM, so your app costs money even when idle. For sporadic-traffic projects, Deno Deploy's model is cheaper. For steady-traffic apps, Fly.io's always-on VMs can actually be more predictable.

Ecosystem maturity. Fly.io has been around longer, has more community content, and supports a wider range of use cases. Deno Deploy is newer and more focused. The Deno ecosystem is growing but still smaller than Node's. If you need a specific npm package that doesn't work in Deno, that's a potential blocker.

When to Choose Fly.io

• Your app uses Python, Go, Rust, or any non-JS/TS language
• You need persistent file storage or full system access
• A managed relational database should be part of the platform
• You want full VM control over your runtime environment
• Your application has system-level dependencies

When to Choose Deno Deploy

• You're building TypeScript-first APIs or web applications
• The fastest possible deployment cycle matters
• Near-zero cold starts are important for your use case
• KV storage covers your data needs, or you're fine with an external database
• The free tier's 100K daily requests fits your traffic

The Verdict

These platforms serve overlapping but distinct audiences. Fly.io is the general-purpose edge platform that runs anything. Deno Deploy is the specialized TypeScript edge platform that runs lighter and faster.

If you're a TypeScript developer building APIs, server-rendered sites with Fresh, or lightweight web applications, Deno Deploy is the faster and cheaper option. The deployment speed alone is worth it. Push code, it's live everywhere in seconds. No Docker, no builds, no waiting.

If you need the flexibility to run any language, need persistent storage, or need a relational database on the same platform, Fly.io is the right choice. The VM model is heavier but gives you freedom that V8 isolates can't match.

My recommendation for TypeScript developers: try Deno Deploy first. The free tier is generous, deployments are instant, and KV handles many data needs. If you hit a wall where you need more runtime flexibility, Fly.io is the natural next step. For everyone else, Fly.io is the default because Deno Deploy simply doesn't support your stack.