PostHog vs Fly.io
Open source product analytics — all-in-one dev tool
vs. Run your app close to users, globally
Pricing tiers
PostHog
Free (generous)
No credit card. Each product has its own free monthly quota. Great for startups + OSS.
Free
Paid (usage-based)
Pay only what you use, after free quotas. Volume discounts at higher tiers. 6 projects, 7-year retention.
$0 base (usage-based)
Self-Hosted (OSS)
MIT-licensed. Run on your own infra via Docker/k8s. Zero vendor lock-in.
$0 base (usage-based)
Enterprise
Custom. SAML SSO, dedicated CSM, custom SLA.
Custom
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
Free-tier quotas head-to-head
Comparing free on PostHog vs pay-as-you-go on Fly.io.
| Metric | PostHog | Fly.io |
|---|---|---|
| data warehouse rows | 1000000 rows/month | — |
| error tracking exceptions | 100000 exceptions/month | — |
| feature flags requests | 1000000 requests/month | — |
| llm analytics events | 100000 events/month | — |
| logs gb | 50 GB/month | — |
| product analytics events | 1000000 events/month | — |
| projects | 1 projects | — |
| retention years | 1 year | — |
| session replay recordings | 5000 recordings/month | — |
| surveys responses | 1500 responses/month | — |
| team members | unlimited members | — |
Features
PostHog · 14 features
- A/B Testing — Experiments with significance analysis.
- Data Pipelines — Export events to BigQuery, Snowflake, S3.
- Data Warehouse — Query external sources (Stripe, Hubspot, S3) alongside events with SQL.
- Error Tracking — Sentry-style error tracking in same platform.
- Feature Flags — Rollout flags with targeting, A/B testing, JSON payloads.
- LLM Analytics — Tracing + cost tracking for OpenAI, Anthropic, Gemini, etc.
- Logs — Centralized log ingest with free 50 GB/month.
- Product Analytics — Events, funnels, trends, retention, paths. SQL insights available.
- Revenue Tracking — Integration with Stripe for revenue + churn metrics.
- Self-Hosting — Docker/Helm. Full feature parity with cloud.
- Session Replay — Watch user sessions. Privacy controls, masked inputs, JS errors.
- SQL Query API — Run ClickHouse SQL over your events via API.
- Surveys — In-app surveys + feedback widgets.
- Workflows — Trigger emails/webhooks on events.
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.
Developer interfaces
| Kind | PostHog | Fly.io |
|---|---|---|
| CLI | — | flyctl CLI |
| SDK | posthog-android, posthog-flutter, posthog-go, posthog-ios (Swift), posthog-js, posthog-node, posthog-php, posthog-python, posthog-react-native, posthog-ruby | — |
| REST | PostHog REST API | Machines API |
| GRAPHQL | — | Fly GraphQL API |
| MCP | PostHog MCP | — |
| OTHER | Webhooks + Actions | Fly Postgres (wire) |
Staxly is an independent catalog of developer platforms. Outbound links to PostHog and Fly.io are plain references to their official websites. Pricing is verified against vendor pages at publication time — reconfirm before buying.
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