TL;DR
Fly.io is a secure edge platform using Firecracker micro-VMs for strong isolation. It provides private networking (WireGuard-based), encrypted secrets, and runs your apps close to users globally. The VM-level isolation is stronger than container-based platforms. A solid choice for latency-sensitive and globally distributed applications.
What is Fly.io?
Fly.io runs applications on micro-VMs at edge locations worldwide. Unlike container platforms, it uses Firecracker (same technology as AWS Lambda) for stronger isolation. Great for globally distributed apps, real-time features, and latency-sensitive workloads.
Our Verdict
What's Good
- Firecracker VM isolation
- WireGuard private networking
- Encrypted secrets management
- Automatic HTTPS
- Global anycast routing
What to Watch
- CLI-centric (steeper learning curve)
- Volume encryption setup
- Network complexity
Firecracker Isolation
VM-Level Security: Fly.io uses Firecracker micro-VMs, providing stronger isolation than containers. Each app runs in its own VM with a dedicated kernel.
| Isolation Type | Fly.io (Firecracker) | Container Platforms |
|---|---|---|
| Kernel | Dedicated per VM | Shared with host |
| Escape risk | Very low | Low (but higher) |
| Resource isolation | Hardware-enforced | Cgroup-enforced |
Private Networking
Fly.io's private networking uses WireGuard:
- 6PN (IPv6 Private Network): All your apps can communicate privately
- WireGuard tunnels: Encrypted connections between regions
- Flycast: Private load balancing within your network
- No public exposure: Internal services stay internal
Connect from Anywhere: Use fly wireguard to connect your local machine to your Fly private network for development and debugging.
Secrets Management
| Feature | Description |
|---|---|
| Storage | Encrypted at rest |
| Access | Only at runtime, in VM |
| Management | fly secrets set/unset |
| Rotation | Update triggers redeploy |
Database Options
- Fly Postgres: Managed Postgres with automatic failover
- LiteFS: Distributed SQLite at the edge
- Volumes: Persistent storage for self-managed databases
- Upstash/Turso: Third-party edge databases
Is Fly.io safe for production?
Yes, Fly.io's Firecracker VM isolation is the same technology AWS uses for Lambda. It provides stronger security boundaries than container-based platforms. Many companies run production workloads on Fly.
Is Firecracker more secure than containers?
Yes, Firecracker VMs provide better isolation. Each VM has its own kernel, making container escape vulnerabilities irrelevant. It's the gold standard for multi-tenant isolation.
How does private networking work?
All your Fly apps share a private IPv6 network. Communication between apps is encrypted via WireGuard. External traffic goes through Fly's proxy with automatic HTTPS.