CrabTalk vs Fly.io.
Machines + persistent storage
Fly Machines run application code in configurable virtual machines, with volumes and managed database options. CrabTalk runs a narrower Rust/Wasm tool service with small per-call reservations and service-owned SQLite.
Which fits your work?
CrabTalk
- Small tools with independently sized memory budgets
- SQL state and agent access in one service
- Deployable templates with hosting usage per run
Fly.io
- An existing application or container runtime
- Processes and dependencies beyond Wasm host APIs
- Machine sizing, placement and networking control
Use both.
An application on Fly.io can call a CrabTalk service over HTTP for a reusable integration or shared tool operation. Keep its existing database when the application already owns the relevant records.
Capabilities side by side.
| Capability | CrabTalk | Fly.io |
|---|---|---|
| Runtime | Rust compiled to WebAssembly | Application processes inside Fly Machines |
| Memory scope | 1–128 MiB reservation per tool call | Configured memory per Machine, shared by application requests |
| Input-specific sizing | Lower one call’s reservation in code | Size Machines and manage application concurrency |
| Persistent data | SQLite with deploy-time migrations | Volumes for local data or managed/external databases |
| Tool endpoint | Hosted MCP discovery and calling | Host your HTTP or MCP server |
| Dependencies | Wasm-compatible code and host APIs | Application frameworks and container dependencies |
| Billing scope | Calls and resources within account limits | Machine runtime, storage, networking and other resources |
Host a shared inventory tool.
Two agents query inventory and update a reservation. Compare a new small tool service with the server you may already have, including its existing data.
CrabTalk
- Define inventory tools and SQLite migrations
- Set tool budgets and caller access
- Deploy and connect both agents
Fly.io
- Reuse the existing server or package a tool server
- Connect its database or persistent volume
- Deploy Machines and configure access and capacity
CrabTalk vs Fly.io pricing.
CrabTalk
Runs, CPU, reserved memory-time and rows. A call can lower its reservation when the input needs less memory.
Fly.io
Started Machines are billed by runtime and selected size. Volumes, stopped-Machine storage, data transfer and other resources can contribute even when no tool calls arrive.
Size and price the complete Fly application at its expected utilization. Multiple requests share Machine capacity; Fly.io is outside our isolated-call calculator.
Limits that affect the choice.
- CrabTalk tools have at most 100 ms CPU and 128 MiB memory. Docker dependencies, subprocesses and heavier computations require another runtime.
- Fly Volumes are local to a server and attach to one Machine. Include replication and recovery requirements when designing a SQLite deployment.
- This page compares Fly Machines. Fly.io’s Sprites are a separate product with a different lifecycle and billing model.
Questions about CrabTalk and Fly.io.
Can Fly.io run a persistent SQLite service?
Yes. A Fly Volume can hold a database file. Compare its deployment, backups and multi-Machine design with CrabTalk’s service-owned database.
Does each request pay for a separate Machine allocation?
No. An application can serve multiple requests from one Machine. Estimate total Machine runtime and utilization, rather than multiplying a VM’s memory by every overlapping call.
Can I move a container directly to CrabTalk?
No. The code must use Rust/Wasm host APIs and fit tool budgets. Keeping the server on Fly.io may be simpler when its runtime and dependencies already meet the need.
Sources.
Checked .