Railway starts at $5/month for the Hobby plan; Fly.io starts free. That pricing difference alone drives a lot of comparisons, but the more important difference for apps built with AI coding tools is the isolation model: Railway uses Docker containers and Fly.io uses Firecracker microVMs, the same hypervisor AWS uses for Lambda.
TL;DR
Railway is simpler and cheaper for small apps, with strong environment isolation and a visual UI. Fly.io costs more at scale but provides VM-level isolation, a global edge network, and dedicated IPs. For a typical vibe-coded app, Railway is the faster path. If your app runs in multiple regions or handles sensitive multi-tenant data, Fly.io's architecture is worth the overhead.
Platform Overview
What Is Railway?
Railway is a deployment platform focused on developer experience. It runs applications in Docker containers with a visual interface for managing projects, environments, and services. Railway emphasizes quick deployment from Git repositories with minimal configuration.
What Is Fly.io?
Fly.io runs applications on Firecracker microVMs, the same technology AWS uses for Lambda and Fargate. Applications deploy globally to edge locations for low latency. Fly provides more infrastructure control including dedicated IPs, private networking, and custom machine configurations.
Security Feature Comparison
| Security Feature | Railway | Fly.io |
|---|---|---|
| Isolation Technology | Docker containers | Firecracker microVMs |
| Private Networking | Project-level | WireGuard-based |
| Edge Deployment | Limited regions | Global edge network |
| Dedicated IPs | Not available | Available |
| Secret Management | Encrypted variables | Encrypted secrets |
| Database Encryption | At rest and transit | At rest and transit |
| SOC 2 Compliance | Type II | Type II |
Isolation Security
Railway Container Isolation
Railway uses Docker container isolation with standard Linux namespaces and cgroups. Containers are effective for most workloads but share the host kernel with other tenants. Railway's infrastructure adds additional security layers, but container escapes remain a theoretical concern.
Fly.io MicroVM Isolation
Fly.io uses Firecracker microVMs, which provide VM-level isolation with a minimal attack surface. Each application runs in its own VM with a dedicated kernel. This stronger isolation is particularly valuable for multi-tenant platforms or applications handling sensitive data.
Network Security
Railway Private Networking
Railway services in the same project communicate over private networks without internet exposure. Internal DNS resolves service names automatically. This simplifies secure inter-service communication but is limited to project scope.
Fly.io WireGuard Networking
Fly.io uses WireGuard for private networking, providing encrypted communication between your machines globally. You can connect your local development environment to your Fly network securely. The flexibility is greater but requires more networking knowledge.
Pricing Comparison
Pricing differs significantly at each tier:
| Tier | Railway | Fly.io |
|---|---|---|
| Free | No (Trial only) | Yes (limited compute + storage) |
| Entry paid | $5/month (Hobby, includes $5 credit) | Pay-as-you-go from ~$2/month |
| Team | $20/user/month (Pro) | $29/month (Launch) |
| Egress | $0.10/GB | $0.02/GB (lower) |
| Database | Included add-on | Separate Fly Postgres machine |
| Bandwidth billing | After 100 GB free/month | After 160 GB free/month |
Railway's $5 Hobby credit typically covers a small app with one service and a database at low traffic. Fly.io's pay-as-you-go model can be cheaper if your app is idle most of the day, but it's harder to budget.
Choose Railway when you want simple deployment without deep infrastructure knowledge. Railway's visual interface and environment management make security configuration straightforward. Best for teams that prioritize developer experience and don't need edge deployment or VM-level isolation.
Choose Fly.io when you need stronger isolation, global edge deployment, or more infrastructure control. Fly's Firecracker VMs provide better security boundaries. Best for apps requiring low latency globally, multi-tenant SaaS, or workloads with strict isolation requirements.
Best Practices
- Use private networking for all internal service communication
- Store all secrets in encrypted environment variables
- Enable automatic TLS for all public endpoints
- Restrict database access to private networks only
- Use health checks to detect compromised services
- Review access permissions and team roles regularly
Is Firecracker isolation worth the complexity on Fly.io?
For most applications, container isolation is sufficient. MicroVM isolation becomes valuable for multi-tenant SaaS, applications handling sensitive data, or when regulatory requirements demand stronger boundaries. Evaluate based on your threat model.
Can I get dedicated IPs on Railway?
Railway doesn't currently offer dedicated IPs. If you need static IPs for firewall rules or compliance, Fly.io is a better choice. Consider using Cloudflare in front of Railway as an alternative.
Which platform is cheaper for a small app?
Railway's Hobby plan at $5/month with a $5 credit often covers small apps entirely. Fly.io's free tier is more generous on compute hours but charges separately for persistent storage. At low traffic, both land around $5-10/month.
Which platform is better for global applications?
Fly.io's edge deployment provides lower latency globally with applications running close to users. Railway has limited regions. For latency-sensitive applications, Fly's global network is a significant advantage.
Secure Your Deployment
CheckYourVibe scans your deployed app for exposed secrets, misconfigured headers, and open endpoints, whether you're on Railway, Fly.io, or anything else.