AssemblyAI vs Fly.io
Best-in-class speech-to-text API — Universal models, 99 languages, low-latency streaming
vs. Run your app close to users, globally
Pricing tiers
AssemblyAI
Free Credits
$50 in free credits on signup. Full API access.
Free
Pay-as-you-go
Per-hour billing by model. No minimum.
$0 base (usage-based)
Enterprise
Custom contracts. SLA, private deployments, BAA.
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-trial on AssemblyAI vs pay-as-you-go on Fly.io.
| Metric | AssemblyAI | Fly.io |
|---|---|---|
| No overlapping quota metrics for these tiers. | ||
Features
AssemblyAI · 11 features
- Advanced Prompting — Streaming with disfluency + code-switching + realtime diarization.
- Audio Intelligence — Sentiment, topic detection, summarization, entity detection, content safety, IAB…
- Auto Punctuation — Smart capitalization + punctuation.
- Keyterm Prompting — Boost accuracy for domain vocabulary.
- LeMUR (LLM framework) — Run LLMs over transcripts: Q&A, summary, action items.
- Medical Mode — Specialized for clinical + medical vocabulary.
- PII Redaction — Auto-redact credit cards, SSNs, addresses, emails.
- Pre-recorded Transcription — Upload audio/video URL or file → transcript.
- Realtime Streaming — WebSocket-based low-latency STT.
- Speaker Diarization — Identify who spoke when.
- Webhooks — Auto-notify when transcription finishes.
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 | AssemblyAI | Fly.io |
|---|---|---|
| CLI | — | flyctl CLI |
| SDK | assemblyai-go, assemblyai (Node), assemblyai (Python), assemblyai (Ruby) | — |
| REST | AssemblyAI REST API | Machines API |
| GRAPHQL | — | Fly GraphQL API |
| OTHER | Streaming WebSocket, Webhooks | Fly Postgres (wire) |
Staxly is an independent catalog of developer platforms. Outbound links to AssemblyAI 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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