Fly.io vs Vercel: Container Hosting vs Frontend Platform

Fly.io and Vercel are both modern cloud platforms but they are not really competing for the same workloads. Vercel is a deployment platform built around the serverless and edge model, optimised for frontend frameworks and particularly Next.js. It handles build pipelines, preview deployments, CDN distribution, edge middleware, and serverless function execution. Fly.io is a container orchestration platform that deploys Docker images to a global network of VMs, running your application as persistent Machine instances close to your users.

The key difference is workload type. Vercel is stateless by design: functions execute, return a response, and stop. Fly.io supports stateful workloads: a VM starts, stays running, maintains connections, and can write to a local disk. This makes Fly.io suitable for backends, long-running processes, WebSocket servers, and databases that cannot run on a serverless model. Fly.io operates in over 30 regions worldwide. A shared-CPU, 256 MB VM costs approximately $1.94 per month if left always-on, making it substantially cheaper than equivalent serverless compute for steady-state workloads.

Vercel created Next.js and ships new Next.js features with first-party platform support. Incremental Static Regeneration, React Server Components, Partial Prerendering, Next.js Middleware, image optimisation, and server actions all run with zero configuration on Vercel. The platform handles the infrastructure decisions that Next.js features require, such as the routing between edge and serverless runtimes, without developer input.

Fly.io can host Next.js via Docker, but the deployment process is more involved. You need to write a Dockerfile, manage the build process, configure environment variables, and handle the lack of Vercel-specific optimisations such as image optimisation and ISR caching. Edge Middleware does not have a direct equivalent on Fly.io. For teams whose primary concern is Next.js feature completeness and deployment simplicity, Vercel has no practical equivalent. For teams that want more control over how their Next.js application is served, or want to co-locate it with a backend service, Fly.io is a viable alternative.

Vercel's serverless model imposes hard constraints that eliminate entire categories of backend workloads. Functions have a maximum duration of 5 minutes on the Pro plan (extendable for streaming). There is no persistent in-process state between requests. WebSocket connections are not supported in the standard serverless runtime. Long-running background jobs, queue workers, and database services cannot run on Vercel at all.

Fly.io supports all of these workloads because it runs actual persistent VMs. You can run a WebSocket server, maintain in-memory state between requests, write to a local SQLite database, or keep a background worker polling a queue. Fly.io also offers managed Postgres with high availability starting at $38 per month for a basic configuration, and persistent volumes at $0.15 per GB per month for applications that need local disk. Teams building a full-stack application often deploy their Next.js frontend on Vercel and their backend API on Fly.io, using each platform for what it does best. This split architecture is a common and practical pattern.

Vercel's Pro plan costs $20 per developer per month. A team of five developers pays $100 per month before any usage charges. The Pro plan includes $20 of usage credit, 1 TB of bandwidth, and 10 million edge requests. Compute for serverless functions is billed on CPU time, with edge functions limited to 50 ms CPU time per execution. Exceeding included limits triggers overage charges that can surprise teams with high traffic or complex server-side rendering.

Fly.io uses pay-as-you-go pricing with no per-seat fees. A shared-CPU, 256 MB RAM VM running continuously costs approximately $1.94 per month. A dedicated single-CPU, 2 GB RAM VM costs approximately $15 per month. Persistent volumes cost $0.15 per GB per month. Starting January 2026, volume snapshot storage is also charged. There is a soft free allowance for tiny applications with monthly usage below approximately $5. For teams with steady-state backend workloads, Fly.io's per-VM pricing is significantly cheaper than Vercel's serverless compute at equivalent resource levels.

Vercel's serverless functions experience cold starts when a function has not been invoked recently and the runtime container needs to restart. Cold start duration varies by runtime and function size: Node.js functions typically start in 100-500 ms, while larger functions or those with heavy dependencies can take longer. Edge functions run in a lighter V8 isolate environment and start near-instantly but are constrained to a subset of Node.js APIs and cannot run arbitrary npm packages.

Fly.io's always-on VMs have no cold starts. A VM that is perpetually running responds with no boot latency. Scale-to-zero configurations, which stop VMs when idle to save cost, do introduce cold starts when traffic resumes. For latency-sensitive applications, Fly.io's always-on model avoids the unpredictability of serverless cold starts entirely. Fly.io's global network deploys your containers to the nearest region to your users. For APIs serving a global user base, the combination of no cold starts and regional proximity produces consistently low latency that serverless platforms can match on edge functions but not on standard serverless functions.

For most frontend and full-stack web applications built on Next.js, Vercel remains the default. The zero-configuration deployment workflow, first-party support for every Next.js feature, and strong CDN and edge network make it the lowest-friction path from code to production. Teams that need to ship quickly and are comfortable with the serverless model will find Vercel the more productive choice.

Choose Fly.io when your application has backend requirements that the serverless model cannot serve: persistent connections, WebSockets, long-running processes, or stateful workloads. Many production teams use both: Vercel for the frontend, Fly.io for the API or database tier. Fly.io is also the better choice for containerised deployments of non-Next.js applications, or for teams that want fine-grained infrastructure control without the complexity of AWS or GCP. The pricing advantage of Fly.io is clearest for steady-state backend services where always-on VMs are cheaper than equivalent serverless compute over time.