Fly.io vs CircleCI
Run your app close to users, globally
vs. Fast, configurable CI/CD with Docker, ARM, GPU runners and orbs
Pricing tiers
Fly.io
Pay-as-you-go
No monthly fee. Machines billed per second. Free allocations: ~3 small shared machines + 3 GB volumes.
$0 base (usage-based)
Shared CPU 1x — 256 MB
Entry VM. 1 shared vCPU, 256 MB RAM. ~$2.02/month continuously on.
$2/mo
Performance 1x — 2 GB
Dedicated 1 vCPU, 2 GB RAM.
$32/mo
Reservation — Shared (1 yr)
$36/year for $5/mo credit (40% savings).
$36/mo
Shared CPU 8x — 16 GB
8 shared vCPU, 16 GB RAM.
$89/mo
Performance 16x — 128 GB
Dedicated 16 vCPU, 128 GB RAM.
$1014/mo
Enterprise
Custom. Dedicated capacity, SLA.
Custom
CircleCI
Free
$0. 6,000 build minutes/mo (Linux medium). 30 users. Unlimited projects.
Free
Performance
$15/mo (3 users). Credit-based: 80K-240K credits/mo bundles. More concurrency.
$15/mo
Scale
$2,000/mo+ (custom). High concurrency, self-hosted runner support, SSO.
$2000/mo
CircleCI Server
Custom. On-prem deployment of CircleCI. Enterprise only.
Custom
Free-tier quotas head-to-head
Comparing pay-as-you-go on Fly.io vs free on CircleCI.
| Metric | Fly.io | CircleCI |
|---|---|---|
| No overlapping quota metrics for these tiers. | ||
Features
Fly.io · 14 features
- Auto Stop/Start — Machines auto-stop when idle, start on request (like scale-to-zero).
- Certs — Let's Encrypt + wildcard certs managed.
- Fly GPU — A100/L40S/A10 on-demand GPU machines.
- Fly Kubernetes (FKS) — Managed Kubernetes on Fly machines.
- Fly Machines — Firecracker microVMs. Start in <1s. Run any Docker image.
- Fly Postgres — Managed Postgres via Supabase partnership (2024). Also legacy self-run Postgres …
- fly-replay headers — Route request to another region at app level.
- Fly Volumes — Persistent SSD attached to a Machine. Encrypted at rest.
- Global Anycast — Single IP routes to the closest region automatically.
- LiteFS — Distributed SQLite with primary/replica across regions.
- Private Networks — 6PN WireGuard mesh. Connect machines across regions privately.
- Secrets — Encrypted env vars propagated to all regions.
- Tigris (partner) — S3-compatible storage for Fly apps. By partner.
- Upstash Redis (partner) — Managed Redis via Upstash.
CircleCI · 17 features
- ARM + GPU Runners — ARM64 + T4 GPU resource classes.
- .circleci/config.yml — Single source of truth (YAML 2.1).
- Contexts — Org-scoped shared env vars.
- Deploy Markers — Track deployments + rollback.
- Docker Layer Caching — Reuse Docker layers.
- Dynamic Config — Generate config based on changed paths.
- Manual Approval — Gate workflows with manual step.
- Matrix Jobs — Parameterized parallel jobs.
- Orbs — Packaged reusable jobs + commands.
- Parallelism — Split a job across N parallel containers.
- Rerun with SSH — SSH into failed job.
- Restricted Contexts — RBAC for secrets.
- Scheduled Pipelines — Cron-triggered runs.
- Self-Hosted Runners — On your infra.
- Test Insights — Flaky test detection + trends.
- Test Splitting — By timings, filenames, classnames.
- Workflows (DAG) — Fan out, fan in, conditional.
Developer interfaces
| Kind | Fly.io | CircleCI |
|---|---|---|
| CLI | flyctl CLI | circleci CLI |
| REST | Machines API | CircleCI REST API v2 |
| GRAPHQL | Fly GraphQL API | — |
| OTHER | Fly Postgres (wire) | .circleci/config.yml, CircleCI Orbs Registry, CircleCI Webhooks, CircleCI Web UI, Self-Hosted Runner |
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