Fly.io

Fly.io was co-founded by Kurt Mackey, a veteran of the infrastructure world who previously helped build Compose.io (which was acquired by IBM). Kurt and his team approached the cloud with a "developer-first" mindset, frustrated by how difficult it was to simply run a Docker container in multiple regions at once. They didn't want to build another Heroku; they wanted to build something that solved the "latency problem" of the modern internet.

The company is famous for its engineering transparency. Their blog is widely read in the tech community not just for product updates, but for deep-dive technical essays on networking, distributed systems, and the weird challenges of running physical hardware. This culture of "showing their work"—even when things break—has earned them a fiercely loyal following among backend engineers and system architects.

Headquartered in Chicago but operating remotely, Fly.io is backed by top-tier investors including Andreessen Horowitz (a16z) and Intel Capital. Despite their growth into a major cloud player, they have maintained a "hacker" ethos. They are heavily involved in the Elixir and Phoenix communities (providing arguably the best hosting experience for those frameworks) and are constantly pushing the boundaries of what is possible with edge computing and distributed SQLite databases.

Fly.io is squarely aimed at Backend Developers and Systems Engineers who want control without the headache. If you love Docker and want to deploy your container to 30 cities with a single command, this is your home. It is particularly popular with developers using "full-stack" frameworks like Phoenix (Elixir), Rails (Ruby), and Laravel (PHP), as Fly.io provides the persistent storage and networking capabilities these frameworks need to thrive globally.

In 2026, Fly.io has also become the default choice for AI Engineers. Because AI models (like LLMs) are heavy and require GPUs, running them on standard serverless functions is often impossible or too slow. Fly.io allows these engineers to spin up machines with massive GPUs for just a few minutes to process a task, and then shut them down. This "ephemeral GPU" capability makes it perfect for startups building AI agents that need to be fast and cost-effective.

• • Global Apps: If your users are in Brazil, Germany, and Japan, Fly lets you place servers in all three locations instantly.
• • Real-Time Apps: Perfect for WebSocket servers, multiplayer games, and collaboration tools that demand low latency.
• • Database Lovers: Teams that want to run distributed databases like LiteFS (SQLite) closer to the edge.

Fly.io turns a Docker container into a global application. Its primary capability is Multi-Region Deployment. With a simple configuration change, you can tell Fly to run 2 instances in New York, 3 in London, and 1 in Sydney. Their internal load balancer automatically routes user traffic to the closest healthy instance. This isn't just "caching" like a CDN; this is your actual application logic running right next to your user.

A standout feature is the 6PN (IPv6 Private Network). Every app you deploy on Fly.io gets added to a private, encrypted mesh network. This means your web server can talk to your Redis cache or your database securely without ever exposing those ports to the public internet. It simplifies microservices architecture immensely because you don't have to manage complex VPNs or firewalls; "it just works" via internal DNS.

For storage, Fly offers Fly Volumes. These are slices of NVMe drives attached directly to your specific server. Unlike cloud network storage (which can be slow), these are local and incredibly fast. This makes running databases like PostgreSQL or MySQL highly performant. In 2026, they also introduced Sprites, which are specialized, sandboxed environments designed for running untrusted code or AI agents that need to wake up, do a job, and vanish instantly without managing a full server lifecycle.

• • Machine Learning: Access to powerful GPUs (like A100s) on demand for training or inference tasks.
• • Fly Proxy: An intelligent edge proxy that handles TLS termination and connection balancing before traffic even hits your app.
• • Clustering: Easy setup for Elixir/Erlang clusters or clustered databases that need to synchronize across regions.

Fly.io operates on a Usage-Based Pricing model, which is different from the flat fees of Render or Vercel. You pay for exactly what you use: CPU seconds, RAM gigabytes, and disk storage. For example, a tiny VM might cost roughly $1.94 per month if you run it 24/7. However, if you configure it to "auto-suspend" when no one is using it, you might only pay pennies.

They categorize their pricing into plans for support and features. The Hobby Tier is pay-as-you-go. New users often get a small amount of trial credit to get started, but there is no permanent "free forever" tier for new signups in the same way Vercel offers. This is because you are reserving physical hardware resources (RAM/CPU) that cannot be oversold.

For businesses, the Launch Plan ($29/mo) is the entry point. This covers email support and allows you to provision resources in high-demand regions. The **Scale Plan ($199/mo)** is for serious production workloads, offering HIPAA compliance options, SOC2 audits, and priority support. It’s important to remember that these monthly fees are for access and support; your actual infrastructure usage (the servers you run) is billed on top of this fee.

• • Compute: Billed per second. A standard shared CPU with 256MB RAM is very cheap (~$2/mo).
• • Bandwidth: You pay for outbound data transfer (Egress). Internal traffic between your Fly apps is free.
• • Volumes: Persistent storage is billed per GB per month, similar to AWS EBS.

Fly.io is powerful, but it has a steeper Learning Curve than its competitors. It assumes you know how Docker works. You need to understand concepts like fly.toml configuration files, exposing ports, and health checks. If you just want to "upload a zip file" and have a website, Fly might feel like overkill. It is a tool for engineers, not just web designers.

A critical detail is Volume Pinning. When you create a persistent storage volume, it is created on a specific physical server in a specific building. If that specific server has a hardware failure, your database goes down. Fly does not automatically replicate your data to another server for you; you are responsible for setting up database replication (like Postgres read replicas) if you want high availability. This "close to the metal" reality means you have to think more like a sysadmin.

Also, watch out for Billing Complexity. Because you pay for raw resource usage, a misconfigured app that enters a crash loop or a process that leaks memory can slowly drive up your bill. Unlike a flat $20/month plan, your Fly bill can fluctuate. It is highly recommended to use their "Prepaid Credits" system or set up strict budget alerts to avoid end-of-month surprises.

The closest competitor to Fly.io is Render. While Render manages everything for you (including high-availability databases), Fly gives you the raw pieces to build it yourself. Render is generally easier to use and has predictable flat pricing, but Fly offers significantly lower latency and more control over exactly where your code runs globally.

Railway is another strong alternative. Railway bridges the gap nicely; it’s easier than Fly but offers more power than Vercel. Railway’s usage-based billing is very similar to Fly’s, but Railway abstracts away the concept of "regions" more than Fly does. If you don't care about running your app specifically in "Paris vs. Amsterdam" and just want it online, Railway is often simpler.

• • AWS Fargate: The enterprise equivalent. It offers similar container capabilities but with the massive complexity (and power) of the AWS ecosystem.
• • DigitalOcean App Platform: A good middle ground. It runs on DigitalOcean’s servers but offers a PaaS-like experience similar to Fly.
• • Koyeb: A newer competitor that also focuses on global serverless deployments and is very similar in spirit to Fly.io.

• Do I need to use Docker? Yes. Fly.io is built around Docker images. However, they provide "Launchers" that can automatically detect your language (like Node, Go, or Python) and generate a Dockerfile for you if you don't have one.

• Is there a free tier? Not exactly. Fly.io offers trial credits for new users to get started, but they have moved away from a permanent free tier to prevent abuse. For long-term use, you should expect to pay a small monthly amount (often less than $5 for small apps).

• Can I host a database on Fly? Yes. Fly has excellent automation for PostgreSQL. It isn't a "managed service" in the traditional sense (you still have some operational control), but they automate the setup, clustering, and failover for you.

• What is the difference between VMS and Machines? "Fly Machines" are the new standard. They are fast-booting VMs that can start and stop in sub-seconds. This is what enables the "scale to zero" capability, where your app turns off when no one is using it to save money.

• How many regions does Fly support? As of 2026, Fly.io supports over 35 global regions, allowing you to deploy your app physically close to almost any major population center on Earth.